After the fight, you will teleport outside. Mount your horse and equip Link with the new weapon - Bow of Light. It's the only weapon capable of hurting this incarnation of Ganon. The task is to ride around the beast and fire at the golden runes on its body. They only become visible when princess Zelda defies the beast, so be watchful; don't waste your chance! The first couple runes are in the side of the enemy; watch out when you're encircling the boss - it fires a powerful beam from its mouth, which can instantly kill the Protagonist.
After shooting the runes on the sides, another will appear on its belly. Close in and fire at the right moment to deal damage. At the end of the fight, Zelda will tell you to fire at the core of the enemy, which is located in its back. It's a characteristic eye, which will appear when the enemy's firing its laser. In order to be able to shoot the eye, you will have to get into the air using the ability to create tornadoes. If you hit the enemy, he will be definitely defeated, and order will be finally brought into the land.
Congratulations! You've just become the hero of Hyrule. This was quite an adventure.