Spells are learned and collected in the Wizard's Companion. They are segregated into Everyday Spells (normally cast out of battle) and Battle Spells cast during battle (or moments of conflict) to attack the target.
The spells that you get from The Fairy Godmother are spells that can only be used by fairies. You can not use these, because they can not be used by humans, only by fairies. The only exception is the Poison Apple spell.