download this image and flash it to a sd card using raspberrypi imager. DO NOT APPLY CUSTOM SETTINGS.
Then insert the sd into the uConsole and let it boot and expand the filesystem it will reboot during this. After reboot, choose a username and password. Enter the command for your device at the prompt. sudo retropie-device uconsole that will set RetroPie up for the uConsole instead of the DevTerm, then reboot. You will be loaded into EmulationStation with almost all emulators and cores that will work on the CM4. You can remove your sd and instert it into a computer and load your roms into the roms folder in the home directory in ~/RetroPie/roms/ after you load some roms, eject the sd and insert into your uConsole.