You can download the update via Firmware Over the Air (FOTA).
The download won’t count against your data bucket if it is downloaded over the AT&T mobile broadband network.
Although there should be no impacts to settings or data, we recommend that you back up all your media files to an SD card or a PC prior to upgrading the software.
Update & verify software
To update the software
Make sure your device is sufficiently charged and connected to the AT&T network.
From the device home screen, tap Menu > Settings > AT&T Software Update > Check for update.
Follow the on-screen prompts to download and install the update.
The device automatically restarts once the new software successfully installs.
To verify the update
From the device home screen, tap Menu > Settings > Phone information.
The device has the latest software if the Software version matches the current update details.