Use a small capacity USB drive (8GB or less is best) formatted to FAT32 .
Unrar the downloaded archive and move the .bin file (often named MST6M181.bin or similar depending on the chipset) to the root directory of the USB. Update: Turn off the TV. Plug in the USB.
Usually provided as a .bin file compressed within a .rar or .zip archive. Installation Method: USB Upgrade. Where to Download
Turn on the TV (or hold the power button while plugging it in).