It's easy! Sign up simply by going to the Battle Room and clicking "Sign in with Facebook" in the upper right-hand corner of the page. You will have to verify the action with Facebook, but only this once. After you've done so, you're in! You'll then be able to conceal your real name by creating an alias on your Profile page and start participating in the Battle Room forum. Your profile page is also where you will find your Notifications - army assignments, transfers, toon placements and, if you're Battle Room material, perhaps you'll even get to command an army of your own.
The Abridged Version
1. Click "Sign in with Facebook" in the upper right hand corner of the Battle Room.
2. Choose an alias on your Profile page.
3. Enjoy your Lauchie status while you're waiting to be assigned to an army.
But don't get too comfortable. You never know when a message may appear saying you've been transferred... or maybe even iced.
Once the armies launch, you'll have the opportunity to earn points by taking part in official forum discussions, doing quizzes, and participating in other Ender News activities. Then, if you're feeling creative, you can help advance your army by joining in on fun challenges which will be announced every month. These challenges can be anything from creating a fan-made movie poster to coming up with your own Battle School-esque recipe. Each challenge you participate in will earn points for your army and for you individually.
Probably most exciting for many of you: you could get your own story published on Ender News! If you have an original story idea, submit an outline to email@example.com and our editors will review and hopefully approve your idea. Possible ideas are background stories about the movie, reports or even photo reports about Ender's Game related events, interviews, personal accounts, and so on. Ask yourself if your story idea is movie related, if it is an original idea, and if you (as an Ender's Game fan) would be interested in reading such a story from another author. If you can answer all three questions with "Yes!" then there is a very good chance that your idea gets approved and your story gets published on Ender News.
Published stories will earn their authors a good number of points as it is directly creating value for the whole Ender's Game community. To keep track, a standings board will be publically viewable at all times. Not only will you be able to see which army is at the top of the standings, but also which soldiers have earned the most points for their army.
So brush up on your skills -- Battle Room Armies at Ender News are coming soon. :)