It's hard to tell from your screenshot, but I assume you're playing it like a normal match game? The system is actually quite different, and about drawing paths through multiple tiles that match your spells.
I recommend going into the options and watching the "casting spells" tutorial. It's animated and shows how to use the starting spells... Otherwise there are some videos out there. Voxandra did a stream which is quite long, but at around 44:40 she explains the rules quite well.