Extract the contents (usually a file named allupgrade_ms848_4G_sos.bin or similar) to the root directory of a FAT32-formatted USB drive. Insert the USB drive into the TV.
Power on the TV while holding the physical button on the TV frame until the upgrade screen appears.
Firmware for these boards is typically hosted on specialized technician forums like Kenotrontv.ru or provided by sellers on platforms like AliExpress . Preparation: Download all required RAR parts.