No matter how you learn the spell, you will still need to complete a small minigame to use it. To complete the minigame, you simply need to trace your wand around a specific pattern before a red light catches up to you. If it does, you need to start over. All spells, how to get...
Hermione: And what may I ask do you plan to do if this comes up in the final exam? Ron: Copy off you? Hermione: No, you won't! Besides, according to Professor McGonagall, we're to be given special quills bewitched with an anti-cheating spell. Ron: That's insulting! It's as ...