It's pretty straightforward. Each Level has videos, documentation and challenges that you need to complete. The goal of the videos is to model and show you how to use a tool, while the challenges give you an opportunity to practice.

Note that you must complete Level 1 before you can move on to Level 2, and Level 2 before Level 3. 

After you complete a Level by passing the certification test, you'll be emailed a certificate and a badge along with a code that will allow you to access the next level test.