Holding the power button while plugging the TV into the wall to trigger the "USB Upgrade" mode. Do you have the other parts of this archive, or
: Since this is "part 05," the firmware will not function unless you have parts 1 through 4 (and any subsequent parts) in the same folder before extracting. Download RT2861P839 3840x2160 MAGIC 55&58 part05 rar
Typically, once you extract the full set of RAR files, you will get a single .bin or .img file. This is usually installed by: Copying it to a FAT32-formatted USB drive. Plugging it into the TV while powered off. Holding the power button while plugging the TV