Previously, in the Beauty Retouching tutorial, we saw how to use two adjustment layers for this, one for the highlights and one for the shadows. In this tutorial, we show how it was done old school. Many Pros are still using this method to shade their final image. Take a look how to Dodge and Burn the alternate way.
This is a very simple technique and takes more skill than understanding. Here we are using D&B(dodge and burn) only on the final image, after it has been completely retouched. See how to do that in the link above.
First open the file in your Photoshop/Elements.
When you do this, your image becomes visible again. This gray layer is your 'canvas' for D&B. The tools are shown below.
Lets try dodging first. Select the dodge tool(range should always be midtones) and keep the exposure setting to not more than 20%. Paint on the areas you wish to make lighter, for example the area below the eyes, cheek and chin highlights, forehead and nose highlights(if they are flat), white area in the eyeballs etc.
These are good start points, but you should really know how to shade, and judge on image to image basis. This book is quite popular and should help you develop that skill: