Landing page that redirects to forum

[eeeee]

Im sure I wont be the first person to ask this.
I need to have some extra info on a landing page, where people can login before going to forum page.
Im a moderate coder, so know how to get input fields. But then how do I pass username & password to the forum page to login automatically? I did see there is a tutorial for landing page but that didnt seem to have login function?
For security, is it better the landing page hashes the password and only passes that through in hashed format?