2 - Set foreground color to black and select the Brush Tool. Scroll down the list of brushes until you find a brush edge you like. Increase or decrease the size of the brush to the size you want your border edge. Try a couple of stokes until you get something you like. To draw a straight edge, move the brush to a corner of the new window. Hold down the Shift key and drag to the next corner or just click the brush tool in one corner, let go and bring the brush to the next corner and hit the Shift key. That'll also draw the border in a straight line from point to point. Continue until all four edges are completed.
Create a new border/edge file folder to save it in, then name and save your new border/edge as a jpeg file.