Open the downloaded .rar file and copy the .bin file to the root of a FAT32-formatted USB drive.

Typically a single BIOS .bin file contained within a .rar archive. Download Sources

Groups like "lcd tv led tv smart tv software" frequently host collections of these .rar files, including resolutions like 1366x768 . How to Install (USB Method)

How to fix TV main board with usb firmware update software guide