1. Please follow section 4 of "PreBuilt_OS_Image_Installation_Guide.pdf".

Set up the boot mode of the board as "serail download mode".

2. Please follow section 6 of "PreBuilt_OS_Image_Installation_Guide.pdf"

Use USB-OTG installer tool to program eMMC.

3. Please follow section 4 of "PreBuilt_OS_Image_Installation_Guide.pdf".
Set up the boot mode of the board as "Boot from eMMC".

4. Reboot.