MyBB Community Forums

On my forum when i click admin this pops up: Forbidden
You don't have permission to access /admin/index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

anyone know how i can fix it?

Check the CHMOD permissions of your forum root, admin directory, and index.php within the admin directory.

See http://docs.mybb.com/1.8/install/#file-permissions for reference.

If that doesn't work, it seems like the other cause of this, in my experience, has been improper file ownership. If you're on shared hosting, this would most likely be something for the host to solve.