The update is available via the Samsung Kies update software; it will not be offered as an over-the-air (OTA) download, Samsung said.
Those who do not have Kies can get it via Samsung's website. Once installed, Galaxy S III users should visit Samsung's support site, connect the device to the PC, and follow the steps at the bottom of the page.
For Windows users, the update will work on XP, Vista, Windows 7 and 8, but not Windows 8 RT. Macs must be running OS X 10.5 to 10.7. Samsung recommended that devices be fully charged before starting the upgrade process because "the upgrade process may not complete if the charge level is less than 50 percent."
"Android 4.1 makes your phone easier to use and more powerful than ever," AT&T product manager Ryan Lee wrote in a blog post. "The many new features include Google Now, enhanced notifications and several camera updates such as the ability to pause and resume while recording and the low light photo mode, which offers improved picture quality for low light and indoor photos."
Lee also talked up the Pop Up Play update, which "allows users to resize or pause the picture-in-picture video window," and the new Blocking Mode, which lets customers disable incoming calls, notifications, and alarms for a designated period of time.
For first-time smartphone users, meanwhile, Easy Mode simplifies the user experience, while the Swype keyboard enables easier typing and texting.
Samsung said in earlier October that its flagship smartphone would get the Jelly Bean upgrade "soon." Sprint was the first U.S. carrier to roll out Android 4.1 Jelly Bean to the Galaxy S III in late October. The smartphone is also available from T-Mobile and Verizon, as well as smaller carriers like U.S. Cellular and MetroPCS.