1Gather parts and prepare the foot stool
Open the stool flat and slowly drill holes for the 35mm arcade buttons using a 1" Forstner bit.
2Test the buttons
Mount the buttons on the stool and practice clicking them. This is important; do not skip this step. This is a good time to measure out lengths of wire for the buttons.
3Wire that puppy up
4Print all the things
Print the tray that holds the board and the locks for the two sides of the foot stool that keep it from being able to collapse.
5Unleash the circuit snek
Plug in your stool with a micro USB cable. It will show up as a drive. Navigate to this drive and open main.py in your favorite text editor. Mine is Notepad++.
Copy and paste my main.py into your main.py and save it. The code will automatically upload to your foot stool. If everything is cool, the onboard LED will swirl in a rainbow fashion. If it blinks blue/red, something is wrong. It's probably just that copy/paste introduced a tab where a space should be, and the snek only likes spaces.
If this makes no sense, check out the Adafruit guide.