Go into the folder called Makelangelo-firmware and open Makelangelo-firmware.ino with the Arduino app.

The Arduino app is available from https://www.arduino.cc/en/Main/Software

You may be asked to update some features of Arduino. Please follow the prompts and get up to date.

You should see many tabs at the top of the app. If you have only one tab then Arduino has created that folder and moved the ino file into the folder. Quit Arduino, move the rest of the files into the new folder, and re-open the file.