If you have a Mac, you probably are already familiar with the process of using iMovie, but if you aren't there are many tutorials online.
The most important part with iMovie is the video compression.
To properly compress your video:
(1) click File --> Share --> Theater.
(2) At the prompt, click on "Add on This Computer".
(3) iMovie will then start compressing the file.
(4) When complete, just click on the file from iMovie and drag to desk top.
The final size of your video should be about 10 MB/min of video