Look for the latest "Firmware Update" in the Downloads section.
Place the firmware file in the root directory (not inside any folders). Power Down: Turn off the TV and unplug it from the wall.
Once you have the file (usually extracted from the .rar to a .bin or .upd format), follow these steps:
While many third-party sites offer .rar or .zip archives of Sony firmware, the safest route is always the portal.