To configure Ammo which will be used by your abilities you have to follow this short guide
1. Create Item with Ammo type
2. Set parameters like damage, quality, stack limit, and name.
3. Create an ability with Ammo Used and set how many our Arrows you will want to use by this ability
4. Create an item with an effect UseAmmo and select ammo type: Arrow
That’s all if you will use the ability with the created weapon it will consume arrow ammo. You should drag the arrow ammo to the ammo slot in the character window in game.