Open the spell book (located between the armor and ring slot) choose the spell you want then drag it to an open space on your quick bar.
Still Good Still enjoying this, even though it's gotten way too easy. I hit god-status at around level 200, when I found a a talisman that raised the damage on my already pretty good chakram by 1032 points. Haven't used a health potion, cast a spell, or changed weapons since then. What item brought you to invincibility?
Yes it does get easier if you just ramp up the gear. I dont finish many games these days but I enjoyed my play through of this one. I found the Banish spell to be a bit over-powered, I dont think I used a health potion either for a long time. Good game, impressive from a smaller scale developer.
Just an FYI for fellow power levelers out there. Save yourself a lot of time (and IAP) and dont bother grinding. All grinding up levels does is in essence open more gem dumps. Because the dungeons and monsters level with you, there is no point in grinding higher. Once spells are unlocked the best you can do is level it up to your level.