MYBB LOGIN PAGE

Im using mybb1.8 but idk how can i setup a page when people can login and cant acces forum without login. Can u send me a script like:
In default index: if not log on resirect to login.php and if u logged in(cookie) or u write yr id pw to login site redirect to index and u access it?
it was an example coz idk how can i solve it xd
Sorry for bad english