T-Mobile has finally begun rolling out the Android 4.4.2 update to their LG G2 devices earlier this morning. This update will be available over-the-air, so you should be receiving an update notification once it hits your device. At the same time, you can also manually check for the update by going to Settings > General > About phone > Update center > System Updates> Check now.
If you want to learn more about the update, you can head down to T-Mobile Support page as well.