Assuming that you mean the shading on the sim’s skin, this might illustrate it, the before and after editing of my last post:

as you can see, most of the lighting came from in-game lighting, set up with a blank room with a plain wall. Lighting is made with Buhudain’s Invisible Lights. Just set multiple lights to achieve your desired lighting. Then, I edit the colors a bit, etc in Photoshop, and finally use the Burn and Dodge tool in Photoshop to lighten and darken parts of the skin.

Be careful not to over-burn or over-dodge the skin! It’ll look horrible.