Start with your cropped image. Here I have used a 4x6 image at 300 dpi.
Select All
Edit
Stroke/outline, set width (I have used 2 px for this sample), select color (I have used a light gray here), set to inside.
You should now have a stroke outline around your image. Ctrl-D to deselect. You will end up with an image that looks like this.
Customize the stroke outline in width and color to your taste.
Proceed to Border 2