Re: How to create a photo that when placed in a video the background of the video will show

1. File > New document with a transparent background (denoted by the checkerboard pattern).
2. Select the white background from your first image, using the Magic Wand tool. 
3. Go to Select > Inverse.  You should now see marching ants all around your main image.
4. Optionally, you may want to refine edges with the Refine Edge tools.  
5. When you're happy with the selection, drag or copy & paste it into your new transparent document. 
6. Save for Web as PNG-24 with transparency.  See screenshot below.

Nancy O.