I've picked up a few books/ gems that have power for certain classes but I can't seem to equip these items. Anyone know how to? or just having them in the inventory is enough?
Yes. If the PC has such an item in their inventory, and if they are -- or if they add -- one of the classes that can use it, then the item's stat bonuses (and penalties, if any) will automatically kick in.
Speak softly, and carry a big stick. Or better yet: a big, sharp blade.
