Enable cheats in the option then simply click on the skill you want to level up in the status page
Uhm sorry I want to know in spells menu I just forget about it
You can't cheat with spell directly, instead, cheat with the sexen, clicking on its value to get max value (with cheats enabled again), then buy them from Lily at the shrine like usual. You need to have unlocked Lily's spell shop of course.
