Copy the files ukeeb.py, boot.py and main.py to the root of your board, and then create a file matrix.py for your particular board based on the examples.

By default the keyboard will only come up as USB HID keyboard, but if you hold down the key on the first row and first column while connecting it, the CIRCUITPY drive and serial REPL will become available.

CircuitPython at least 7.1.0-beta2 is required.