After the events at the castle, Link must head to the Minish Woods to obtain the treasure of Deepwood Shrine.
Travel to the Minish Woods
As you go south from the castle, you will encounter some enemies. Smith gave you Smith's Sword, which you can use to attack the enemies.
Keep going south and you will reach a roadblock, so go east and you will find some short trees. Cut these down and you can go east to the next area.
You will reach Lon Lon Ranch. From there, go south until you can't go farther south, then go east to reach the Minish Woods.
Explore the Minish Woods
The straightforward path through the forest will take you close to the Deepwood Shrine, but before you get there, you hear a voice cry out for help. Before you go to investigate the voice, keep going west to find a Piece of Heart.
Now go back the way you came. Kill the Octoroks to save the weird green creature, whose name is Ezlo. Try to walk around, and Ezlo will try to keep up with you. Keep walking around until Ezlo hops onto your head. From now on, you can press Select to get advice from Ezlo.
Go back toward where you were when you heard Ezlo's cry for help. When you reach a sparkling tree stump, Ezlo explains how to shrink to Minish size. Walk onto the tree stump and press R to do so.
If you want to return to normal size, stand next to a sparkling portal and press R. Be careful when Minish-sized, because you will drown if you walk into a puddle, and you are more vulnerable to monsters, and grass is too tall for you to walk through. Some floors are too tall for you to go past. While Minish-sized, you can talk to animals, but cats will attack you.
Follow the path west through a log. You will reach an area of water with a couple of lilypads floating around. Carefully step onto a lilypad as it passes, then get off at the north side. Go north and you reach a path with large acorns and leaves. Keep going north and you enter the Minish Village.
Minish Village
Go north and there will be a cutscene. Unfortunately, you don't understand Minish language. Go to the north part of the village to find a bridge over some water. Go north across the bridge and enter the building with blue hexagonal roofs. Inside, talk to Festari, the only Minish who speaks human language. He tells you to find the Jabber Nut in the barrel house to the south.
Go outside and go to the southeast part of the village. Find the house made out of a barrel, with a bridge leading to the roof of it. Inside, go north and push the southernmost crate to the left or right. Go northwest to find the Jabber Nut. Walk up to it and press R to eat it.
There is a wooden walkway east of the wooden bridge that took you to Festari's abbey. If you follow it, you find a Piece of Heart.
The Elder's house is to the west of Festari's abbey. Go there and talk to the Elder. He says that you need the four mystic elements to reforge the Picori Blade. He marks on your map where to find all of the elements. He says that the first element can be found in the shrine to the north of Festari's abbey, so go back to the abbey and talk to Festari, who lets you pass.
Back in the woods, you are still Minish-sized. Go straight north through all of the little holes. If you didn't get the Piece of Heart before, you can't get it at this size. You will need to come back later. Go north to enter Deepwood Shrine.