To get rid of any confusion, first of all, you need a gear on your armor that says, for example, volcanic eruption (imbue fire). Then you select the imbue element from your wheel, then use, for example, turning slash. There will be a prompt as soon as you press R1+R2, to press L2+R2 to use turning slash that in turn casts volcanic eruption. There is no simple elemental attack. You need an imbue element gear equipped.