So your friend is talking, and you want another video inside the first video, so it's next to him? Kind of like a news reader?
If so, iMovie can do that easily. You need to enable advanced tools, then drop second video from the events folder on top of the video in the project (the one of him talking), and a sub menu will pop up, and you select picture in picture. You can then change the size and location of the second video to look like it is next to him.