Beyond Jujutsu Kaisen

How to use techniques--  You need to have soul item, to get one, you need to press O. After that you need book with technique, to get one trade with gojo or get one in creative. After that just use C and V to select between learned techniques. Just warning but look into control if it doesn't work.     

Sukuna-- To become Sukuna vesel, you need to eat fingers, to get finger, just kill finger berear yokai that spawns in the game. There is 30% chance to become vesel.

Techniques-- To get technique, trade with Gojo. Right click on him with yen in hand, to get yen, you need to kill Yokais.