1. Take a photo of a silhouette. It is important that there is light behind the figure. It makes it easier to work with later on.
2. Open the picture.
File > Open
3. Duplicate the Layer. It is always important to have a duplicate of the original images to easily go back in case of mistakes.
Ctrl+J or Layer > Duplicate Layer
4. Add a Threshold adjustment to the layer.
Image > Adjustments > Threshold
Use the handle to adjust the black areas and white areas
5. Create a New Layer to paint in.
Click the New Layer button in the Layers Palette or Layer > New Layer
6. Paint in the black and white areas.
7. Flatten the image.
Layer > Flatten Image