Can't do it. You can't edit Revver videos in QuickTime Pro, FCP or iMovie.
Revver locks down the videos.
They explain it on their blog:
By default, when you upload a video to Revver, your video is protected by the Creative Commons license Attribution-NoDerivs 2.5. This means that people are free to share your video (this is how you make money, after all) but that they must credit you as the creator and they cannot change the video without your permission.So if you want people to be able to remix, mashup or sample your video, you'll have to find another hosting service other than Revver.
This doesn't mean that you shouldn't use Revver, just be aware of the restrictions that they place on your videos once they are posted.