How can I take two different pictures and put them together?

Question: How can I take two different pictures and put them together!?

I really need to know how to take a picture (ex: a picture of nick jonas and selena gomez) and make one picture out of two!. I also need to know how to crop (ex: nick jonas's head and selena gomez's head) and add their faces to another picture!. PLEASE HELP ME!!! PLEASE!! PLEASE!!! HELP!!!! HELP!!!Www@QuestionHome@Com

Best Answer - Chosen by Asker:

You change the opactiy in a picute, which should be up the top somewhere to make it SLIGHTLY see through so you can put the 2 on each other, change both rates to get a better effect!.
and the second part

Use a magnetic lasso to go around their heads and then double click when finished and then rightclick>copy or ctrl +c at the same time and then paste them onto another place!

Its easy if you know how to do it!. Need more help!? come ask!Www@QuestionHome@Com

it depends if you're planning on using photoshop, or what kind of application you're trying to use!. If you're doing this in a dark room, you just need to do a double exposure where you overlap too negatives!. i'm guessing that you're just trying to do this on the computer!. well, you need to give a better description of your situation if you want people to know how to help you with that one!. Www@QuestionHome@Com