Here are a few different ways to add borders to images.

V1
Step 1. Get your picture.
Step 2. Make a new layer. (Shft+Ctrl+N)
Step 3. Select all. (Ctrl+A)
Step 4. Select >>> Modify >>> Border (Width: 1 pixels)
Step 5. Fill with a colour. (Choose as foreground color then press Alt+Backspace)

V2
Step 1. Get your picture.
Step 2. Select all. (Ctrl+A)
Step 3. Edit >>> Stroke...
   Stroke: Width: 1 px, Color: Your Choice
   Location: Inside
   Blending: Leave as it is.

BOTH METHODS CAN BE USED TO MAKE BIGGER BORDERS (e.g. 3 pixels)

You should do a polygonal lasso tool one too :P

So thats what it is..Thanx guys !! XD

you can also make a fixed size retengular that's just 2 pix smaller then you main image and then selectinvers and color it, it's no easier but that's how i do it dunno why but i think becous you can easeley add other elements to your border...

yeh i will!

UPDATED AND ADDED ANOTHER WAY