You may wish on the triforce, only after completing the following tasks:

1. Go to Hyrule and getting three spiritual stones as a child.
2. Get you power level up to 10,000
3. Learn the Song of Time
4. Pull the master sword out and become an adult
5. Go around Hyrule as an adult and gather five medallions. The forest, fire, water, shadow, and spirit medallion
6. Go to the temple of time, enter the room where you pull the master sword and play the song of time
7. A blue beam of light will descend upon you and you wil be transported to the temple of light
8. After going to the temple of light and beating it, Raru will teleport you to the unicorn fountain and you will wish on the triforce
9. Whoever happens to be with you must also have the five medallians. If they do they may also wish upon the triforce
10. One wish only per person on the triforce
11. After you wish you are teleported from the unicorn fountain and are dropped off outside the temple of time
12. After wishing on the triforce, all of your medallions are taken from you and they are sent back to the temples