You can download the update via Firmware Over the Air (FOTA).
You must connect your device to Wi-Fi to download the update.
Software update includes:
Upgrades OS to Lollipop 5.1.1 with security enhancements, network connectivity improvements and corrects an error with SD card memory size reporting.
Enhancements to Apps: OK Google voice command now responds from home screen. Email now supports rich text editing, conversation view and allows user to change which account is used when replying. Camera now supports panorama feature. Keyboard enhanced to add number row.
Device Protection: More protection for lost/stolen devices. Lost or stolen device will remain locked until user signs in with their Google account - even if someone erases the device using the factory data reset option in settings.
Newly added applications: AT&T Messages, Amazon Kindle and Onetouch Connect (smartphone pairing feature allows you to send/receive SMS and calls from your tablet via Bluetooth)
Update & verify software
To update the software
Make sure your device is sufficiently charged and connected to Wi-Fi.
From the device home screen, tap Menu > Settings.
Tap the General tab.
Tap About > AT&T Software updates? > Check for updates.
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 > About phone.
The device has the latest software if the Baseband version and Build number match the current update details.