you need to isolate the cut the object from the background first, there are many ways to delete the White background : 1- use the Quick selection Tool , then refine the edges using select -> select and Mask ( or refine edges if you are not on the latest CC 2017 ) then you may press the delete button or use the layer mask 2- select -> color Range , select the white 3- use the magic wand once you have the Transparent background, you can use any background color by creating a New solid Fill below are screenshots to demonstrate that :
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