AT&T pushes big new update to Galaxy S8 and S8+, here is what's changed
There are some new features aboard the latest patch - AT&T has added support for Google's Daydream VR platform and the corresponding hardware, as well as the ability to hide the navigation bar from the screen through a dot icon in order to maximize the screen view. This functionality was initially released by Samsung in June. You can see the old nav bar compared to the new one in the picture below.
The Android security update for the month of August is also included, as well as updates to the UX, Bluetooth, Calendar, Knox, and so on. The entire changelog can be seen in the source links below.
The update is available OTA, but it might need some time to reach all compatible devices. You can check for it manually by going to Settings > About Device > Software Updates. As always, make sure that your phone is sufficiently charged and connected to a Wi-Fi network before proceeding with the patch.