With the Zora’s Sapphire in your possession, Navi will instruct you to return to the Temple of Time, located in Hyrule Castle Town. Make your way back through Zora’s Domain, Zora’s River, and Hyrule Field to Hyrule Castle Town. Once there, head to the northern part of the Market area to find the entrance to the Temple of Time.
Step inside the Temple of Time. You will see the Pedestal of Time in the center of the room.
Approach the pedestal. You will be prompted to place the three Spiritual Stones you have collected – the Kokiri’s Emerald, the Goron’s Ruby, and the Zora’s Sapphire – into the recesses on the pedestal. After placing all three stones, stand in front of the pedestal and play the Song of Time on your Fairy Ocarina. This will cause the Door of Time to open, revealing the legendary Master Sword, the blade of evil’s bane. Walk forward to the pedestal and pull the Master Sword from its resting place.
As you draw the Master Sword, a powerful cutscene will play. It will show Link’s spirit being sealed away for seven long years, while his body continues to age. When he awakens, he will have grown into an adult, ready to face the greater challenges that await him.
It’s important to note that even after becoming Adult Link, you can still return to the era of Young Link. By playing the Ocarina of Time within the Temple of Time after meeting Zelda as an adult, you can travel back in time.
This allows you to complete any remaining tasks or collect any missed items, such as Gold Skulltulas or Heart Pieces, that were only accessible during your time as a child, ensuring a true 100% completion of this portion of the game.