single login

hello
I'm Italian, so I apologize for my English.

PunBB I integrated into my web space, and then made my login on my page I would like the login is valid also for the forum, without having to login again.
In fact, the utilities are the same as the forums and check the table PBB_users.

How do I set my user directly. I just have to interact with cookies (how?) Or do I also set other variables (which?)

Thank