This is a quick easy way that doesn't give good results unless you know how.
1. Load up the picture into Photoshop (I assume you know how to do this)
2. There should be a tool called the magic wand: it's picture is of a magic wand... it's near the top. (If you hold your mouse of the different tools for a few seconds, you'll find what they are called)
3. Click anywhere on the person. depending on what it is set at, it will select either all of the person, too much of the person (some background included) or far more likely not enough of that person.
4a) If it has selected all of the person you are very lucky and you can just press ctrl+c to copy that person, then place where wanted.
4b) If it has selected too much of the person then you'll have to change the tolerance of the magic wand. To do this there will be, in the place that shows you the specifics of the tool there will be a place to change the tolerance. Change to a lower value.
4c) If the magic wand isn't selecting all of them. Change the tolerance up, and/or hold down shift and select other parts of the person. Holding down shift will make it so that the selection adds onto the current selection... you'll see what I mean when you do this.
5. Now you've got the person selected press ctrl+c and paste where wanted.