Showing pages, forums etc in main.php

I was just working with wphpbb wpg2 and a few other things. It’s all working nice, however, is there a way to integrate a page/object anything, into the main.php much like when you click on a ‘gallery’ link it shows the gallery in the main.php. Is there a way to make my php forum show up in my main.php?

Sorry if this doesnt make sense i’ve been working through the night on this.