To add the shadows, I zoom way in on the image, and choose the “Burn Tool” on the tool bar to the left. (The “Burn Tool” looks like a hand.) In the old days of making real enlargements using a piece of film and an enlarger, this techniques was called “dodging and burning”, … a little dance that the photographer would do in the darkroom constantly moving his hands around the image on the enlargement paper while it was being exposed. This little “dance” would “burn in” the area that needed more density and “dodge out” the areas that needed less. Using the “Burn Tool”, you do this in the same way. Carefully and slowly, you run the tool over the areas that you want to “burn in” more shadows. Again, work slowly and carefully!