Here you can find ready-made Pi-KVM images for Raspberry Pi

Download the appropriate memory card image for the Pi-KVM. Select the image by the board, platform, and the video capture device you are using.

Minimum 16 Gb memory card class 10 is strongly recommended.

Raspberry Pi 4, v2 platform:

Raspberry Pi Zero W, v2 platform:

Raspberry Pi 4, v3 shield platform:

To flash the image follow the instructions.
Right now, pre-compiled images are only available for the Raspberry Pi 4 and ZeroW. In all other cases, you will need to build the operating system yourself. But don't worry, it's very simple.
Images archive.