T-Mobile has started the process of rolling out the Android 4.3 update for Samsung Galaxy S 4 devices on their network. The update is available via an over-the-air update if a user is on a WiFi connection or it can be downloaded and installed using Samsung Kies.
According to T-Mobile’s support page, the update brings Android 4.3′s updates along with KNOX and Samsung Galaxy Gear support. To grab the update OTA, just go to Settings –> More –> About device –> Software update. You can hit the source link for more details and information.