megob has it right. The camera actually puts the frame on the paper one step before taking the picture.
When you open the camera door you will see the picture box where the paper is shot at and above that you will have an assembly which holds the pressure plate. The assembly that holds the pressure plate has either 2 or 4 5/16 bolts holding it in place, If the black line is on the top of your picture move that assembly down and if is on the bottom move that assembly up.
One other thing to check is to make sure there is not a "stray" piece of paper stuck inside the picture box.
To address the other commentors note about a light problem. Light leak problems most often manifest themselves as yellow or white unwanted images on the picture.