http://design.tutsplus.com/tutorials/make-a-trendy-double-exposure-effect-in-adobe-photoshop--cms-23774

Here is a link to the double exposure technique.
YES, You may have figured out your own easier way of doing it, BUT I want you to try this method because it has you learning a new tool called a "clipping mask", which you have never used.

You must use all your own photos. You will need 1 simple portrait and 1 natural backdrop. You want your natural backdrop to be kind of "busy" like a bush or tree bark. Look at the examples to see what I mean.