When you visit any forum, you'll see a "search forums" box at the top of the forum. Enter one or more keywords and do a search. Go through the results and click the "advanced search" link under the "search forums" box if you wish to refine your search. If your keywords don't show any results, you'll see a form to do an advanced search. In general, start with one or two simple keywords and then refine your search if you get too many results.