Hello and thank you for posting this question on InPixio support forum.
You may add entire photo into another photo using Photomontage function of Photo Cutter (part of Photo Clip).
Also using the Cutout function of Photo Cutter you can cutout an object from one photo and then move to Photomontage tab where by pressing on the button with plus sign in the middle of it after all backdrop images select image of your choice to place behind the object or entire photo.
Use the buttons around the placed image on the work area to resize, rotate, flip and position it in desired way.
Press on the diskette button above the work area to save the result as new image file.