When it comes to a character that can cast a spell, you click on 'Spell', and it shows the levels you can cast, and what spells you have. But nothing happens when I click on those spells - nothing at all. Am I missing something? They are white, so I'm pretty sure there's nothing stopping me. It just doesn't seem to work.

Try moving the cursor to the spell (using up and down arrows) and pressing Confirm (mapped to 'Z' under default keyboard controls).

That did it - many thanks!!! Now I can actually play this. :)