how do you put one persons face on anothers body?
When ever i try to move my cropped face into the photo to place it, it always makes a new document

cut it out w/ pen tool
make selection
then use your move tool to drag it on to your document.

or if its a seperate saved picture on your comp , go to file at the top left and instead of clicking open click place than load the pic it will start a new layer with the selected picture