Please note Moss is only meant to be used as the foundation for MinUI on the RGB30. Moss is non-functional without an accompanying MinUI SD card.
To install: flash the .img.gz file to the SD card that goes into the left slot (labeled TF-OS) on your RGB30 then continue installing MinUI.
To update: copy the .tar file to the root of the SD card that goes into the right slot (labeledTFGAME) on your RGB30.
In both cases, be patient, it can take upwards of a minute to complete.