The Open Beta features the map "Operation Métro" in the Game mode "Rush".
Full version will contain 8 more expansive maps that adapt to any of the six game modes.
To join the party, download the Origin Client here (~50MB) and download the Beta from within the client.
On Playstation 3, the Beta will automatically appear on the Playstation Network Store.
Similar on Xbox360: It will appear automatically on the Xbox Live Marketplace.
The stats won't be carried over from the Beta to the final game.
Got any questions? Reach out to EA's customer service