You need to do nothing at all, other than create your web site. Bravenet doesn't leave it up to the user to take care of it. They will add all the advertisements that you can possible stand, all by themselves. Initially, your site will be ad free. But after 7 to 10 days, the ad banners will be automatically inserted into your web pages, when users visit your site.
Be prepared, by designing your site to work with the banners. This usually means not to design with frames, or use coding with absolute positioning elements. Frames and absolute positioning elements do not play well with the ad banners.