Open Classifieds and PunBB

Hi, basicly im running PunBB with loads of extentions i did have a classifieds section on my old site (before re done the site using this forum script)

I would like to re intergrate open classifieds back into my site, i would just like to know in general how could create a page with my sites header and footer (with no content inbetween) so i can then intergrate with OC, also this would come in handy to create custom error pages ect.