Right click the background layer in your Layers palette then choose the Duplicate option from the sub-menu. A copy of the background layer will appear in the layers palette. Click the Suntan tool (if necessary) then set the size to a small size, around 11 or to the size of your choice.
TIP: To adjust the brush size quickly while you work, use the shortcut key ALT and drag.
Study your image and find the darkest points of the skin, those parts that appear to orange in step 6. In the sample image, these areas will be around the hairlines and on the upper left most portion of the forehead.