Just to clear any confusion, you do need to register for this forum if you want to post anything even if you already have an account on Colaborator. You can set up your own username and password however you want it and it doesn't have to be the same as your Colaborator login information. The separate registration allows for better moderation of the forum, but once you register you can stay logged in by checking the box saying, "Log me on automatically each visit." That way you can come and go from the forum without having to log yourself in every time.
To register, just go up to the Login button, click it, and there'll be an option to sign up. You'll have to confirm your account in your email, but once you do so, you're all set!
If you have questions, please don't hesitate to ask.