1. "To spell" as in "to say the letters of a word"
* épeler (pronounced eh-peh-lay)
2. "To spell" as in "to cast a spell"
* ensorceler (pronounced on-sor-se-lay)
So, if you want to say "How do you spell this word?", you would say: "Comment épèle-t-on ce mot?"
If you want to say "The witch cast a spell", you would say: "La sorcière a ensorcelé."