How to add banners to left/right side?

Ok, Im trying to find which html page I should edit to put things to the sides of each page. For example, on this website here that we are on, the center of the forums is white, and the outside area around it is black. I would like to put a banner in that black area. I tried adding my banners to different areas on the the templates/tmp_uni/index.html page, but that didnt work. Anybody know where to find the page where you could add banners that would appear in that area Im talking about? Thanks

Most of us would just use the admin=> tools => Banners and add it in there.

Woah thanks a lot. I forgot about that option! that makes things a lot easier lol. Thanks again.