Well, it's not really possible. This is a
fun shop, not a
real shop. This shop is designed for members to have fun, not for any real purchases.
I do not see why you'd want a real shop to be integrated with a forum (unless your members pay for the items by posting).
You're probably looking for something like
CRE Loaded or osCommerce, which are standard eCommerce scripts. You may try
this script to integrate your osCommerce/CRE Loaded installation with your forum.