You can register through the official site. Funcom says it will be welcoming more testers as the phases roll on, and gameplay features and content to test will trickle out progressively as well. An open beta will be available sometime before launch as well, so if you don't get into the closed beta you'll still be able to try it out then.
The debut trailer showed off a variety of minifig characters, each with their own abilities. Funcom is aiming for about 100 characters in all, and you'll be able to choose from among them to make a three-character squad.
"We are heading into very exciting times," said executive producer Lawrence Poe in the announcement. "Closed Beta is first and foremost an incredibly important tool which allows us to receive valuable feedback from our audience, feedback that we can use to improve the experience and make it the best possible game before we launch it to the masses. The whole team is looking forward to opening the door and letting players come in and experience some of the great stories, content and gameplay that we are creating."