Integrating Template Security with Project Security

I just purchased the DocManager Template and want to add it to an existing project.
The existing project has Database security with users table - 'email' is username, 'password' is password and 'full_name' is full name fields.
When I add the DocManager to the project, I did not allow the template to override the project security - the doc_users table was created.
When I log into my project - I am unable to launch DocManager>Files list page from within the project.
How can I use the security on the existing project for DocManager?
Thanks!