Straighten, Square and Crop Photo's of Old Photos

[amyearsley]

I've taken a load of photo's of old photo prints. They are not square on the photo's I have taken and some of the photos were not completely flat.

What I want to be able to do is select the four corners of the photo, square up the corners and crop to that size so end up with a nice square off straight photo.

I've tried searching but have been unable to figure this out. Any help would be appreciated.

Thanks
Andrew