You don't need to buy photos from us. But use the app to prepare them so we know what image you want to use. For instance, if you want to use a 5x7, select your video, and crop it how you want for the size you prefer. Then tap the "download" icon above the photo. Your photo will be registered as a MagicPhoto and you can display it or print it however you want. Print it at home, take it to a one hour photo place, whatever.
Or let us print it for you to save you the trouble!