Re: How to edit CSS of forum?
Find the elements in the page that you wish to apply new styles to, then add those styles to the style.css in your bbPress template folder.
I find the web developer toolbar by Chris Pederick invaluable for this sort of thing. You can hover over the item, find out the class or ID, then edit the CSS while still viewing the page. Then, once it does what you want, make the edit permanent in your style.css.