Warframe is currently in Closed Beta, which means the only way you can access the game and all this sweet, new content is if you have a beta key. Lucky for you, we just got a lot more beta codes to give out to all of you!
Comment on this page either using your GameZone account or Facebook account. You'll then receive a Beta Key in your Private Messages. (Keep a lookout for an email alert)
Once you obtain your Beta Key, go to www.warframe.com/signup to Create an Account or to Finalize your Account if you reserved on Warframe.com previously (note: please use the exact same email address and alias you reserved earlier)
Check your email! Warframe will send you an email with a link that will authenticate your account and bring you to the BETA KEY ACTIVATION PAGE (note: check your junk folder too)