In case people don't know, the magic shots are ones in which Disney adds something to the photograph. Common examples including holding Tink in the palm of your hands, Stitch jumping out of the ground into your picture, and Mickey or Minnie sitting next to you on a bench. There are a host of others I haven't covered and probably some I've never even seen.
The magic shot elements are automatically added to your picture. You do not need to add them yourself at home, but you can add additional borders to the magic shots if you want to. Viewing the photos in the park does not start the 30 day clock ticking. While you do not need to view the photos in the park, I highly recommend doing so. Photopass pictures can and do go missing. Disney can usually find these, but it's much easier to do so when you have other examples of the shirts, hats, et all people were wearing in the picture and have a CM looking right at other pictures (and people) of your group. Your best bet is to go when the photo store is not crowded, so morning is usually a great time.
I also had a case where one of my magic shots wasn't working. The photograph was there, but the magic part was missing. It was quite easy for them to get it working right then and there. It may be harder to do so after you're home because you're trying to describe something that a person on the other end of the telephone may not be able to see.