Rockpis-v12-spi2-waveshare35c image file

I’m trying to use Waveshare 3.5" RPI LCD Model C with Radxa Rock Pi S V1.2 board.
Where can I find and download following Rock Pi S image file as mentioned in the Radxa support website? And I could not find it anywhere.

rockpis-v12-spi2-waveshare35c # Waveshare 3.5inch RPI LCD Model C on SPI2 for ROCK Pi S V1.2

Can you scan the guide,, first? And follow the steps to setup RPI LCD.