Drag your photo inside of the document. Determine how you would like to position your photo. You need to at least be able to see your eyes, nose, and mouth.

Before you start the nose, you will first need to make a large shape for your face.
After you add all of your highlights, go back and add in highlights using a similar method. You will use the value scale, but instead use colors that are lighter.
Start with the shadows that will be a bit darker than your base color and work your way to the really dark colors. OVERLAP YOUR SHAPES!