The NVIDIA Games app comes preinstalled on the new SHIELD TV in the games row.
This app replaces the previous SHIELD Hub apps (SHIELD games, GeForce NOW, and GameStream).
SHIELD TV (2015) owners will get updated to the NVIDIA Games app on a rolling basis over a period of weeks starting January 26th, 2017.
After this update, the SHIELD Hub row will be removed. Until this app update, the SHIELD Hub row will still be present.
If you don't want to wait for the app update, you can choose to join the NVIDIA Games beta community to gain access to the app.