how to change default h1 and h2 font size

I wish to make the font size smaller on the h1 and h2 tags. I currently have TK Google fonts installed (from themekraft) and have set my default title to 31 because this is as small as I want the title, but the h1 and h2 are huge.

Supposedly the TK google fonts is supposed to overrule the other settings but that isn't perfectly the case. I can live with this, but I do want to fix the size and am not sure how to make sure it overrules what is there in other ways.

Maybe an !important tag? (I keep reading about these)