Another simple way
Open the image
use Ctrl+J to duplicate the layer ( layer1)
Then click on the background layer to turn it into a Layer (0)
Go back to layer 1 and make a selection ( Making sure feathering is about 70px)
On the menu bar chose : Select, chose inverse, then hit backspace, then deselect
You will see that a feathered selection now appears on layer 1
Then go back to Layer 0 and vary Opacity to determine how much background you want to show.
You may delete layer 0 , that will leave you with a white border ( May or may not be desirable) or better leave it if you prefer a subtle (Vignetting its called)
If you are happy with the results, merge the layers and flatten the image
Once you do it a few times it will become second nature
Good luck
A subtle example
This is what happens when you delete layer 0