It won't install since you have a custom recovery. Need stock recovery to install OTA's.
---------- Post added at 06:06 PM ---------- Previous post was at 06:01 PM ----------
From the AT&T site
The size of the update file is 57 MB and is available for download via Wi-Fi.
EAS Fix (Enable Data Encryption Policy in the device via over the air)
Enhanced Google Map
Fix-to correct AT&T Messages name display issue within AT&T folder on the Home screen (wrapping of "s" to the second line)