Even if you haven't received your email from BioWare yet, if you registered or already qualified to beta (stress) test this weekend, you can visit swtor.com/tester to RSVP for the event and begin downloading the game client. Begin downloading early, the game is over 20 GB in size, and there is probably, literally, a million other people having to do the same this week. Don't expect to just get it all done within a few hours before the test begins!
You must log into your SWTOR account before you see the following. Expect to be asked your preset account security questions upon login to both the website and the game client.