remove background image on video

Hi,
I need to remove a red fire alarm image on a video presentation. It's part of the video and shows up the whole time. But once the image is removed, I need to make sure that there is no white spot in that area. I'm using iMovie'11 version 9. I don't know how to edit it using this software. Which video editing tool should I use to remove this image? Other suggestions are welcome. Thank you.

What are you expecting to be there instead of a "white" image? If that fire alarm logo is embedded in the video, you can't simply remove it and expect whatever there was in the background to show back up.

You need video software with the ability to track an object and overlay a texture. Final Cut Pro and Adobe AfterEffects are the two that spring to mind. You will also likely need a plugin or two to accomplish this task to a reasonable level. TrackX is a great plugin for FCP and Adobe AE

FCP: https://www.apple.com/final-cut-pro/
Plugins: TrackX Powered by Mocha

Note: When talking about visuals, it wouldn't hurt to upload a still of the video to show what you are looking at.