if you plan to integrate photopost with vb3, then it is a good idea to have your forums installed first. this would prevent you having to redo anything later since we depend on the user system for identification and there isn't a photopost->
vb importer.
http://www.photopostdev.com is a good example site of PhotoPost integrated with vb3.
PhotPost works as a standalone, too; but as I said, if you plan to integrate, its best to do that from the start.