How do you use soulstones in Oblivion

if they have a soul in them, then get into the arcane university and use an altar of enchanting to put enchantments on your normal weapons, or equip them in the inventory to recharge weapons that already have an enchantment. if they have no souls in them, you can cast a soul trap spell on a creature (only black soul gems can contain humans) and kill the thing you casted the spell on while it's still in effect. if you do that, you will trap the soul in the gem. now go and enchant. oh, and you can enchant armour and clothes, too.