How do I use sea soul stones to level up heroes?

Tap the hero icon to go to the hero screen and then select the hero you want to level up. You can only increase the level so far in each season so make sure it is one that has not reached the max level yet.

Tap the + icon on the right of the ?heroes level and then you will see the number of 'single piece' books that you have and the sea soul stones.

When you Level up the game will use the single piece books first and the sea soul stones last when the books run out.

For more questions for Sea of Conquest check out the answers page where you can search or ask your own question.