font size comments & reply

Hi,

I've been trying to change the font size of te 'leave a reply' (among other titles) where people can comment to posts en react onthe comments etc.
I've tried the tips on this forum, but nothing I've tried has worked. I've tried to:
- change the settings in the post&pages area (header and footerboxes)
- insert css (I was'nt sure about which box to put is in, so tried 'em all but none worked)
- style & configure comments
- body, text & links area
- deavctivate the few plugins that I use.

I'm obviously doing something wrong, but have no idea what. Anyone who can help?

I'm using atahualpa 3.7.24

Thanx!