The newest version of Android, 4.4.2 KitKat, is making its way onto AT&T Samsung Galaxy S4s right now. Itching to try out the latest that Google has to offer? Keep an eye on your status bar for a notification letting you know that a system update is ready.
Some of changes you can expect, aside from an upgrade to KitKat, are Samsung Galaxy Gear compatibility, the ability to drag and drop to uninstall or disable apps, and call reliability improvements.
If you don't see the notification yet, you can manually fetch the over-the-air (OTA) update. Head to your GS4's Settings -> More -> About device -> Software update -> Check for updates, then press OK at the bottom.
You'll need to be on a Wi-Fi connection (you can't update over mobile data), and as the update can use 412 MB to 842 MB of storage (depending on your current Android version), have at least 850 MB of free space on your device.
It also wouldn't hurt to have a fully charged battery, or just keep your phone plugged in, so it doesn't run out of juice in the middle of the update.
It may tell you that your software is already up to date, and to check back in 24 hours. While you're limited to checking for updates once every 24 hours, you can use a little softModder trick to get around that. Head to your GS4's Settings -> More -> Date and time.
Uncheck the box for Automatic date and time, and you'll be able to set the date manually. Simply forward the clock a day and you'll be able to run the software check again. Just don't forget to set it back to automatic time once you're done getting the update.
If you're rooted (most likely on 4.3 or 4.2.2), you might not want to update to KitKat quite yet. For one, OTAs and modded phones don't play well with each other. If you do download the OTA, it'll probably fail during installation. Secondly, on the off chance that you do get the update to work on your GS4, you'll lose root.
My advice? Hold off on updating until this build of KitKat has been rooted. It's only a matter of time until developers find a way to root, and we should be able to get some flashable Odin files to manually upgrade to KitKat.
But stay tuned—when the rooted version of the update is released, we'll have your download link and instructions here.