Let me show you one way to do this. I will use a Filter to create the deckle edge.
Layer 1. I opened the photograph that I want to have a deckle edge. I have already done all the straightening and what else I wanted on the photo. All I want is to put the deckle edge around it.
Layer 2. I duplicated Layer 1, Command / Control- J, for this layer. I do this so if I make a goof I still have the original layer still there.
Then I turned off the visibility of Layer 1 by clicking on the eyeball at the front of the Layer 1. I selected the Rectangular Marquee Tool and made a selection just a little in from the edges of the photo in the border area.
Then I clicked on the button at the bottom of the layer panel to add a layer mask. This adds the layer mask to Layer 2. We want the mask to be white so that it shows the area inside the marching ants. If yours came in as black, that is, hiding the area inside the marching ants, use Command / Control - I to invert it and change it to white. Make sure the mask is selected, by clicking on the mask thumbnail, when you do that. You can see the transparency behind the photo.
Make sure the mask is selected. Then go to Filter / Distort / Glass.
This opens a large dialog. Here is the right hand side of the dialog. In it you adjust the Distortion, Smoothness and Scaling sliders to give you the look for the deckle edge that you want.
In this case, I have Distortion 8, Smoothness 11, and Scaling 152%. This seems to work well for me for this 7 x 4-inch, 300 ppi, photograph. Actually, you see the image while you make your adjustments with the sliders so you see what you are doing. In the following image, I have adjusted the size of the image so it all fits in the area of the dialog. You can change the size by clicking in the bottom left of the dialog where it says 100% and open the choices. I selected fit in view.
Then I clicked OK. So you can see the deckle edge more easily, I have put a layer filled with black below Layer 2.
Now, if you want to use the deckled edged photo in a layout, you can just drag its layer onto your layout and use it there. If you are going to use it in another layout, I would recommend making the photo the size you want it for the layout before you add the deckle edge. That way you will see how the edge looks for that size photo.
Hope this helps you in your scrapbooking.