Prestigio PMP7079D QUAD Technical & Service Manual page 25

There are two ways to upgrade the firmware. The firmware's name must be
named as "update.img". Copy it to the root directory of SD card.
One way:
1. Insert the SD card and power on the device, it'll pop up a dialog window as
shown below after the device boots completely.
2. Click "Install", then the device will update the new firmware and reboot
automatically.
All manuals and user guides at all-guides.com
Firmware update guide (SDcard)