You can only install Photopost and integrate it with a forum you actually have on the server. You will get problems trying to play.
If you install Photopost and select SMF integration there are fields that appear that ask you to set the SMF cookie which needs to be set for things to work. After you install you can set a switch in admin forum option in photopost to use forum styles and it will pull your forum style.
I would delete everything and start fresh.