Photoshop CS2 HELP?

When you press F7 in Photoshop you will get open a small layers window. where your image layer is shown,, 1st select your image/layer shown in small window.. now see the bottom left some " f " sign click it and select stroke ( you have to fill stroke for borders.. if you want square go for input if you want round corner go for outer. playaround and you will get it).