T-Mobile Galaxy Note 2 multi-window update now live
This update (surprisingly) made it to Verizon first, but now T-Mobile users can enjoy the Note II's multi-window system, which allows users to have two apps running concurrently in separate windows on the same screen. It's a great way to use the huge screen of the Note II.
To check for your update just head to Settings --> About Phone --> Software Updates.
source: Droid Life