It is pushed OTA (over the air) and via Samsung Kies
It looks like Samsung has finally kicked off the rollout of the long-awaited Android 4.1.2 Jelly Bean update for Galaxy S Advance.According to XDA Developers forum user areeb47, the update is now pushed OTA (over the air) in India. Galaxy S Advance owners can also upgrade to Jelly Bean via Kies desktop software.
Those who have yet to be notified on the update should wait a few more days, as Samsung usually rolls out these major upgrades in waves, so not all users receive it at the same time.
Jelly Bean update has been confirmed to bring improved performance for Galaxy S Advance devices, along with lots of new features and services, such as Google Now, Expanded notifications, Direct call and more.
For more details on how to manually download and flash the official Android 4.1.2 Jelly Bean ROM for Galaxy S Advance, head over to the original thread.