Fortify Magicka can be found in the forms of a spell in the skill set of Restoration or Enchanting. It is used to enhance the overall amount of magicka one can posses at once. It can be found in the wild, bound to armor and accessories. It can be put onto weapons through an Altar of Enchanting, however this will enhance the magicka of anything you hit with the weapon, not the wielder. Magnitude of enhancement is dependent on the spell cast, or the enchantment. It can also be determined by the armor you are wearing at the given time, should you be inexperienced in it.