STEP 1
Open your image in Photoshop



STEP 2
Select the rectangular marquee tool from the top left of the toolbar. Click on the top left corner of your image and drag the rectangle all the way to the bottom right corner. It might take a couple attempts before you get your border to be the size you want. If you make a mistake, click on right button on your mouse and click on
Deselect



STEP 3
From EDIT - STROKE and



You will get something like this



You need to pick up: width, color, and location
First time it is inside then you do again
Edit – stroke but your color will be black and location will be inside
Then again right click deselect and put that layer on overlay
You will get this beautifull semi – transparent border



You can put white inside or outside
Same as black. There is there is a difference between them.
Try it