First, download the skeleton archive (.zip) and unzip it.

It has the following structure:

├── initial_design.html  # initial HTML template
├── public/
│   ├── bootstrap/ # bootstrap sources
│   ├── images/
│   └── style.css  # main stylesheet
├── server.py      # server-side application
└── templates/     # Jinja templates

To test, open initial_design.html in a browser. It should look similar to the following screenshot:

Also, it would be a good idea to test your Python / Flask setup:

python3 server.py
# it should say that the server is running on http://127.0.0.1:5000/