Install latest version of python: https://www.python.org/downloads/
Type python into Command Prompt/Terminal. If that doesn't work, check out: https://projects.raspberrypi.org/en/projects/using-pip-on-windows/4
(You can also try py if that doesn't work)
Next, run pip install Flask and clone this project (or copy and paste the file contents).
To run your project, run flask --app Main --debug run in the console