Here's your Suggested Homework Assignment:
From the reference I've provided or from your imagination, practice the Three-Step process provided in the training.
Do it, at first, on very simple construction and them ease into more challenging ones.
1. Draw the Shape of Form
2. Draw the Shape of Shadow on the Form
3. Give the Shadow a dark Value and...
4. Squint at what you you've drawn to see if all the Shadows group together against all the Lights.
Have Fun, my friend!