Record from Camera makes it simple to import video to iMovie directly from your webcam. Access it through the camera icon in the center left of the screen, or through File>Import from Camera.
Before import, you need to decide where to save the new file, and which event to file it in. Also, you can have iMovie analyze your new video clip for recognizable faces, and stabilize it to remove any camera shakiness.
More: Webcam recording tips
