create a new layer (ctrl+shift+N)
Select all (ctrl+A)
With the marquee tool selected (M) right click and select 'stroke'
Choose 1px, 2px, however thick you want and the colour and make sure 'inside' is selected.
For a 'black, colour, black' border. Make sure the first stroke is 3px black. Then stroke again 2px of a colour of your choosing. Then another 1px black. All 'inside'.
'Cinematic' borders (like the one i have now in my Machida sig) is a border that only borders the top and bottom. Use the Marquee tool (M) and drag from one side to another as thin or thick as you want and fill it with black (in a new layer)
Then duplicate that layer (ctrl+J) and drag it to the other side.
I much prefer a simple 1px border, or even no border at all. Or a thin border that doesn't distract the eye. But it's all preference