Are you unsure how to use Jeanine's Edge Overlays? Here are some ideas.
1. Drag the overlay over a photo. You may want to resize your photo to 12x12 to begin with, or you will have to resize the edge overlay to fit onto the photo and then crop. You can use blend modes, change the hue or saturation, or apply layer styles to the edge overlay.
I like how this photo looks with one of the Grunge-It Edges from Volume 1 turned white by moving the Lightness slider all the way to the right in the Hue/Saturation dialogue box (hit Command/Control - U).
Or how about with "Painted Wallboard," one of the default Layer Styles in PSE? It is accessible by clicking on the Layer Styles icon, circled in red beside the number 1 below, and clicking open the drop down box (2) to select Patterns. Scroll to find the pattern you want and either double click on it or hit the Apply button(4).
2. The edge overly is perfect for 12x12 papers, of course, because it is 12x12. You might also apply it to smaller pieces of paper for journaling or matting. In my layout below, I used the overlay on the background paper, applied a Hard Light Blend Mode, and reduced the opacity to 30% to make it more subtle. Blend Modes are found in the drop-down box at the top of the Layers Palette.