After you have all eight Triforce pieces, you can enter the final dungeon. Get prepared, then go save Zelda!

Get Prepared

Buy a red potion.

Go get the bomb upgrades from dungeon 4 and dungeon 8 if you haven't already. Each one costs 100 rupees.

Get the Magic Book from dungeon 4 if you haven't already.

Get the Magical Sword if you haven't already.

Go to the Dungeon

Dungeon 9 is in the northwest corner of the map. The easiest way to get there is to use the whistle until you are in an area with a white building and a bunch of Armos Statues. From there, go south, then east, then northeast, east, north, west, north, and then west until you reach a dead end. Bomb the north wall a couple of squares east of the stairs to open the dungeon. Go in.

Get the Silver Arrows

Go north. If you don't have all the Triforce Pieces, you won't be allowed in. If this is the case, you will have to go back to whichever dungeon(s) you haven't completed so you can get the remaining Triforce piece(s).

Otherwise, the doors will open for you. Go north, but be careful of the spike traps in the next room. Use the candle or wand to light up the room. Push the middle of the east wall until you go through.

Use the candle or wand to light up the room. Go east through the narrow passage, then push the middle of the east wall to go through.

In this room full of Wizzrobes, bomb the middle of the north wall and go through the hole. You can kill the Patra if you want the map. Then push the middle of the west wall to go through. Kill all the Wizzrobes, then push the block and go down the stairs to get the Silver Arrows.

Get the Red Ring

Go upstairs from where you got the Silver Arrows. Push the middle of the north wall to go through. Avoid the red bubbles, and push the leftmost block. Go down the stairs, and go through the passage until you are upstairs.

Bomb the middle of the north wall and go through. Use the candle or wand to light up the room. Kill the very fast Lanmolas (the wand is very effective if you have the magic book), then go west, but be careful of the spike traps in the next room. Go west from the Like-Like room, then in the room with the Vires go north through the locked door.

Use the candle or wand to light up the room. In the room with the Keese, go west through the locked door. Kill the Lanmolas if you want bombs, then go north. In the room with the red bubbles, bomb the middle of the east wall and go through. (If a red bubble hits you, you will reach a blue bubble soon, so just keep going.) Push the block to the right, then go north, but be careful of the spike traps in the next room. From the room with the Wizzrobes, go east.

In the room with bubbles and Wizzrobes, you can bomb the middle of the south wall and go through if you want the compass. Then go north from the room where you got the Compass.

In the room with bubbles and Wizzrobes, bomb the middle of the north wall and go through.

From the room full of blue Wizzrobes, go east through the locked door. You reach a room with Wizzrobes and Like-Likes. Go through the north door.

The old man tells you to go to the next room. Push the middle of the west wall to go through, but be careful of the spike traps in the next room.

Go west from the room with Like-Likes and spike traps. Then go north to a room with a Patra. Push the middle of the west wall to go through. Kill the very fast Lanmolas (the magic wand with the magic book is very effective), then push the leftmost block. Go down to get the Red Ring.

Go to Ganon

Go back upstairs from where you got the Red Ring. Push the middle of the east wall until you go through. Kill the Patra, then push the leftmost block. Go down the stairs, and go through the passage until you are upstairs.

Bomb the middle of the east wall and go through. Kill the Patra to open the east door. Go east.

Ganon

You will show your Triforce of Courage, and Ganon will appear. Then he will become invisible. There appear to be holes in the floor, but you can walk over them. You can only tell where Ganon is by looking for the fireballs that he shoots at you. Swing your sword where the fireballs are coming from. After you hit Ganon enough times with your sword, he will turn red and be stunned. While he is stunned, hit him with a Silver Arrow to kill him.

Rescue Zelda

Then take the Triforce of Power that he left behind, and go north, kill the fire with your sword, and go to Zelda! Congratulations! You are great!