Step 3 - Lighting
Okay, you can only learn to shade by first finding the light. The blue is where most of the dark appears in the image. The white creates a nice little triangle in this square image (We'll probably go over composition in the near future).
You may block in this area if you wish, but just by knowing it's there will help a lot. We pretty much only need to shade one side of the image. This creates contrast and depth... the whole point of shading.