Ive yet to get around to QMK for the 65% Kit so Ill breifly guide you here on how to use the KMK version

1. Flash circuitpython 6.3.0 to your Raspberry pi Pico
https://adafruit-circuit-python.s3.amazonaws.com/bin/raspberry_pi_pico/en_GB/adafruit-circuitpython-raspberry_pi_pico-en_GB-6.3.0.uf2

2. Download this zip and extract its contents to the root directory of your raspberry pi which should show up as a USB Drive called "Circuitpy" after flashing circuitpython
https://github.com/Envious-Data/Env-KB65M/raw/main/_firmware/65percFW.zip

I have uploaded a beta QMK firmware for the 65% kit but ive yet to properly test it.