I know most of you know how to do this already, but since I just did it only minutes ago with my short film script, "Escalation," I thought I would give you some links and walk you through the process.
It took me 5 minutes to fill out the form, upload the pdf file of my script and register.
This is where you go to register: Click Here
It costs $20 ($10 if you are WGA member).
Just don't screw it up - they won't let you revise your submission.