How can I merge 2 movies in Final Cut Express or iMovie 09 by splitting the screen between them?

I need to have a video of someone in one half of the screen and something else running to their right as they speak. I know it's possible, but I'm a nube at editing so clear, dumbified answers would be appreciated.How can I merge 2 movies in Final Cut Express or iMovie 09 by splitting the screen between them?
You won't be able to do that in iMovie. To do what your talking about, do something similar to this:


http://www.youtube.com/watch?v=O-iGK_n5h鈥?/a>How can I merge 2 movies in Final Cut Express or iMovie 09 by splitting the screen between them?
you may get a video joiner for mac help you merge them into one,


http://www.macyoutubeconverter.com/flv-j鈥?/a>