resizing in layers

to Resize:

In your background photo go to:
Layer
New
Layer

Choose your selection tool, for example, 'Rectangular Marquee Tool' (doesn't really matter which as you will be getting rid of the edges - just don't use 'crop'!)

Go to:
- Edit
- Copy
- Edit
-Paste


Click on Move tool (top icon on tool bar) and move object into background picture (it will automatically open in the new layer)

To resize go to:
-Edit
-transform
-scale
-press shift down and go to the corner of the selected box

Now you can get rid of the part of the selected item that you don't want using layers mask reveal all and paint brush.