The Tom Clancy’s The Division Beta is your chance to test and experience a pre-release version of the game before it launches. Plus, it serves as an important opportunity to make sure that the game is balanced and that the servers are tested to pave the way for a smooth launch. The beta will not be a full version of the game, and will only function during specific time frames.
The Beta begins on January 29th for PC players, and runs through January 31st. (12 am Pacific on the night of the 31st)
PC guide: Here
FAQ: Here