Board Thread:Help!/@comment-24510844-20140206000805/@comment-3509554-20140206044905

On N Terraria 3, you have to open the skills tab, and right click an active spell "have [ ] before the name", then use by pressing C.

On N Terraria 4, move the Active Spell to one of the 4 slots of spell, and activate it by pressing it's key. (Ex:. F4 is my skill's slot, i need to press F4 to use it)

Also, you may use C to cast the last casted spell.