Register for the site, go to the BoI main site, then click Apply for Beta.
You'll get your key immediately(for me atlease) in your mail.
Then, follow the instructions in the mail.
Then wait till the 13th and enjoy
Alright im starting an Agitator5 character on the second server "Onyx" and tomorrow ill be starting a character in BOI also by the same name. I know in DOMO you can be a lot of classes and switch so I wont post my class but im going Heretic in BOI for sure.