The course content is contained in Articles. This post is an example of an Article.
The content contained in an Article could be YouTube videos, audio (podcast episodes), text copy, documents or graphics.
The Training Units are collections of Articles.
The Training Units are ordered chronologically. When the course began in January 2020, I started with the basics.
I suggest that you begin at Unit A1 and work thorugh the Units. I only say this because I sometimes refer to earlier material in the training and you may have to track back to learn more.
However, everyone is different. So... feel free to look through the Units to find whatever training you are interested in.