I've added a link to a Youtube video where it is explained. Anyway, it is easier than what it is shown here...
Do not hesitate to contact me if you want further instructions.
STEP 1: Take the photos with a green fabric or paper on the background.
STEP 2: Look for a image you like on "Google" that fits your story.
STEP 3: Use the programme "Photokey" to edit your images. More instructions on the Youtube Video.

