So the Galaxy S6 is having its moment in the sun, the S5 came out over a year ago, and you're still carrying around an S4 in your pocket. Hey, it makes sense. The S4 remains a competent piece of tech, despite the marketing hype that insists on you having tossed it aside by now.
For you, AT&T is now pushing out Android Lollipop.
This over-the-air update is a little late to the party, but whatever. It pulls down a 947MB file, which you're required to download over Wi-Fi. Afterwards, your device will be left running build number LRX22C.1337UCUGOC3.