Vivid Unit has eMMC storage onboard and the operating system (Debian with XFCE desktop enviroment) has been pre-installed in the eMMC. Usually you do not need to install operating system by yourself. However if the operating system corrupts or you want to install a different operating system, you may follow this instructions.

In order to reflash the OS into eMMC, you need to connect your Vivid Unit to your computer (with Windows installed) via an USB type-C cable. You press and hold the small button in the middle of the board (do not release it) and then tap the power button to start the device. The board will enter MASKROM mode, which allows you to reflash the OS into eMMC.

Run the RKDevTool.exe tool and you should see it says a MASKROM device is found. Click the tab “Upgrade Firmware” and it is the page to flash the new operating system into eMMC.  Click the “Firmware” button to locate and choose the disk image with operating system, and then click “Upgrade” button to flash it into eMMC.