This is a tutorial for adding a border to an image in Photoshop.

1) Ctrl + left click on the layer's thumbnail in the layer toolbox

This will select everything in that layer.

2) Go to Edit > Stoke

A box will appear with different options available. The most important is 'width' which lets you choose the width of your border, in pixels.

3) Choose 'OK'

4) You now have a border!