After you rescue your Loftwing and practice flying, it will be time for the Wing Ceremony.
Race to Catch the Statuette
After a cutscene, the Wing Ceremony will begin. When you see the word GO, hold the dash button to dash off the end of the ledge, then summon your Loftwing. (Note: whenever you want to fly, you have to dash, not walk, off of certain piers and ledges, before summoning your Loftwing. Also, you can't summon your Loftwing at night.)
After you summon your Loftwing, the race will begin. Your objective is to catch the Bird Statuette that the Golden Loftwing is carrying. If you lose sight of it, look for a golden arrow at the edge of the screen. It points in the direction of the Golden Loftwing. Get as close as you can to the Golden Loftwing, and when you are close enough, press the indicated button to take the Statuette. To get close enough, have your Loftwing flap its wings to gain altitude (press the Help button if you don't remember how to do this), then descend toward the golden bird. It is helpful to stay at a higher altitude than the Golden Loftwing whenever possible. You can also press the charge button to speed up temporarily. Press the Help button if you don't remember how.
After you try to catch it, Groose and his henchmen will interfere, so you will have to try again, but this time you have to avoid the eggs that they throw at you. If you get hit, you will slow down for a moment. Just use the same techniques as before while avoiding the eggs. This time you will win for real.
Get the Sailcloth
During the cutscene that follows, Zelda will give you the Sailcloth. It allows you to float downward. While falling, press the indicated button when it appears, to take out the Sailcloth and float to the ground.
Now comes the final part of the ceremony: you have to fall down from the statue and land within the circle on the ground.
As you skydive downward, position yourself within the circle on the ground, then use the Sailcloth when prompted, to float the rest of the way down. If you didn't position yourself properly, you can try again as many times as you need.
Once that is done, watch the cutscene to see what happens.
Afterward, open the cabinet to get another blue rupee.
Then go outside.
Follow the Floating Figure
Follow the floating figure. Once you reach the entrance to the Goddess Statue, the figure will lead you to the right, jumping down some ledges. Continue following until a Remlit (a cat-like creature) attacks you. Just hit it a couple of times with your sword to get it to leave you alone.
Up ahead, there is a narrow ledge on the wall, but before you run up and grab it, drop down to the lower level, kill the Green Chuchu (chop downward to make the two smaller Chuchus go off to the sides so they can't combine into a bigger one again), then open the nearby chest to get a red rupee.
Turn around and go up the ramp to return to where the floating person is waiting. Run up the wall to grab the narrow ledge and go around on your hands.
Let go on the other side and continue down the steep slope. Kill the Keese, then run up the steep stone slope and kill the Keese and Green Chuchu here. Then run to jump over the gap and climb the ledges. Make another running jump to grab the vines on the wall. Climb up.
Continue following until you see a short cutscene. Go through the door in the Goddess Statue.
You will be in a chamber where there is a sword. Approach the sword and there will be a cutscene, where the floating figure introduces herself as Fi (rhymes with "sky"). Walk up to the sword in the pedestal and follow the on screen instructions to remove it. Afterward, point it up, then hold it still to let it charge. If you are having trouble with it, just remember to hold it still and don't move it after you point it up. You now have the Goddess Sword.
During the cutscene, you will get the Emerald Tablet. Go to the crest behind Fi, then hold the sword skyward as before (point the sword up and hold it still until it charges up) then slash the crest with your sword. Go up and examine the slot that appeared. You'll put the Emerald Tablet in place. This will make a column of light appear in the clouds. This is where you will be able to descend to the surface. Before that, though, you should buy some things.
Buy Equipment
After the cutscenes, leave your room, and Fledge will give you the Adventure Pouch. Then go to the far end of the hallway, go out through the double doors, and talk to Professor Owlan to get a free Wooden Shield. Be sure to equip it.
Then head south.
Wii and Wii U Version - Fi Tutorial
In the Wii and Wii U versions, Fi will stop you and say that you can change the on-screen interface. Just press 1, then click the button at the bottom-left where it says Interface. This will change what is shown on the screen when you are running around and doing stuff. The Standard interface shows an outline of the Wiimote with the buttons that you can use, the Lite interface shows the buttons without the Wiimote outline, and the Pro interface doesn't show the Wiimote outline or the buttons.
All Versions
Now go into to the Bazaar, which is the big red building in the center of Skyloft. Talk to Luv (the potion seller) to get a free Empty Bottle. You can buy a potion from her while you are here if you want to, although it helps to have an empty bottle for an upcoming part of the game. Some of the potions are not for sale yet, though. Her husband Bertie can strengthen your potions, but you won't be able to get the necessary ingredients for a while, so just ignore him for now.
There is a woman here named Peatrice who will do Item Check, which means that she will store items for you that you can come back and pick up later. If your Adventure Pouch is full but you pick up an item that would normally go in the Adventure Pouch, it will automatically be sent to Item Check.
There is also a fortune teller named Sparrot, a guy named Gondo who can upgrade your equipment if you bring him scraps and things, and a guy named Rupin who sells various items.
Finish Preparing
If you have a Wooden Shield and you got the Empty Bottle from the potion lady, you're ready to go down to the surface. Go south and go near the tower where you first encountered Groose, and Fi will mention the column of light. (In the Nintendo Switch version, the Fi symbol will light up, so press the indicated button to talk to her if you wish.) When you are ready to go, dash off of the edge, then press the whistle button to summon your Loftwing.
Get a Piece of Heart
If you wish, you can fly to the Pumpkin Landing to get the first Piece of Heart. Just open the map when you are flying on your Loftwing, then look east of the column of light to see an island with an orange shape in the middle. As you fly there, you may see a bird carrying a rupee. You can do a charge attack to hit the bird and get the rupee.
Fly to the Pumpkin Landing and press the whistle button to land on the island. You can use the Sailcloth to help you land safely, if needed.
Go inside of the pumpkin-shaped building, then go upstairs and do a roll attack into the railing (be sure to hit the railing that is closest to the chandelier) until the chandelier falls down and breaks. After it breaks, go downstairs and get the Piece of Heart and the rupees that fell.
Do a Chore for Pumm
Talk to Pumm, the guy behind the counter, after you break the chandelier in the Lumpy Pumpkin. He will say that you need to do work for him so he can afford to buy a new chandelier. His first task for you is to deliver some hot pumpkin soup to Eagus, who is the guy who let you borrow the practice sword from the sparring hall. You need an empty bottle to do this task. If you don't have any bottles, you can get a free one by talking to Luv at the potion shop in the Skyloft Bazaar.
The soup becomes cold after five minutes. Just run off of the edge of the pumpkin landing, whistle to call your bird, then fly toward Skyloft. Fly up to the circular rock with the glowing spot inside. Fly through it to get a speed boost. Then land on Skyloft near the Sparring Hall. Run in and talk to Eagus to give him the soup. Pumm doesn't have any more chores for you yet, so you'll have to come back later.
Go to the Surface
Fly to the green column of light in the sky. When you are close enough to the column of light, press the indicated button to Dive, or fly directly at the opening in the clouds, and you will automatically dive. After a cutscene, you will arrive at the Sealed Grounds.