Hi Beth:
As a general rule it's better to start a new thread for a new topic. (Click the 'Photoshop Q&A' link above and you'll see the 'New Thread" button about 1 inch down and to the left. But no big deal... I found you.
Here are a couple ways to add an edge to your image.
If you have a Background-only image:
* Duplicate the Background so there is a regular layer above the Background
* Layer > Layer Style > Stroke
* Adjust the settings until you like what you see (be sure to choose option "inside")
* OK
Here's another way to skin the cat...
* Layer > New > Layer (Easy to delete the layer if you don't like the results)
* Select > All
* Edit > Stroke
. Pick a color
. Width - your choice
. Blend mode = normal
. Inside is a good choice
. OK
Hope this gets you moving.
~Danny~