If you want to compile the eyes code from source, instructions and a link to the code is here:
https://learn.adafruit.com/adafruit-mon ... ource-codeNote that there are a ton of library dependencies, and you'll need the latest Adafruit SAMD support through the Boards Manager.
The NeoPixels are on digital pin 8, I think. There will be a guide with all the pinouts and such soon, I appreciate your patience.
And yeah, it’s an Arduino project but leverages the flash filesystem (which appears as “CIRCUITPY” whether or not CircuitPython is currently installed on the board) to make customization easier. Access the flash filesystem from Arduino is a recent addition, so the original name stuck.