Photopost integrates with phpbb3 login
Now thanks for the link. For one your gallery is installed as a standalone meaning it is not integrated with anything so your not going to integrate with phpbb3.
If you mean to integrate with phpbb3 you would actually need to install the application to integrate with phpbb3. This is the bulk of your issue and why posting an accurate link to your site is essential because seeing the site I now see why you have an issue.