CustomCSS?

I'm sorry if this is a stupid question but I couldn't find any help on Google.

I need to style (color, size) the 'ADD NEW COMMENT' - but I have no idea how to go about doing that.

I did check out http://wiki.disqus.net/CustomCSS but it doesn't quite make sense to me. what exactly do I do? I created a css file and linked to it....but my problem is the actual css.

this is what I have in my CSS file. and I mean only this:
#disqus_thread #dsq-content h2 { font-weight: normal; }

I'm guessing that's wrong, coz there's no change at all. please help!!