Move it closer to and further away from the subject and watch how the shadow side of the face is filled in. When you get it where you like it, leave it there. This is the mirror, placed in direct sunlight behind and on the opposite side from the main panel. Be careful that the light does not reflect into the camera lens and that it doesn't light the front of the subject's face or cheek. Now you're ready to plop the subject into position and begin taking pictures.
Tips Use a longer lens to keep the background uncluttered and provide a nice perspective.
Try to keep the camera near the subject's eye level. I started taking this picture on my stomach but the fence in the background was distracting. I raised the camera a little higher until I got the clean, dark background I wanted. This makes it easier to set up the fill and edge lights. If the panel is too wide you can turn it at a slight angle.