Instructions
Visit the Temple of Time in Hyrule. Hyrule is, for the most part, the central hub of the game and is a giant castle surrounded by even larger walls. Streets line the outside of the castle, allowing you to access the temple, which is located on the north-east of the city of Hyrule. The temple will be completely empty, except for a large stone with a sword in it at the front of the temple.
Place the sword into the stone to become a child again. To do this, approach the stone and press the "A" button. The Master Sword will automatically be placed into the stone. The game's timeline will instantly switch to its other timeline when Link, the character you play, is still a child.
Visit Zora's Domain. When you are in the past, the area will be unfrozen and you will be able to access the entire area.