Using the workshop guide as a reference, choose which sections interest you and complete their respective problems. Each seciton has a Python file with template code to use. There are also comments indicating where you should write your code. When you've completed the sections you want, you can go back and add type annotations to your functions to make the code easier to understand later.
When working on this section, you will need to have ROS Noetic installed and configured. Additionally, you will need to create a package that contains the code. See the ROS tutorials for creating and building a package. Don't forget to make your Python files executable before running them as ROS nodes.