You don't need Handbrake for that if it is your own DVD.
You need to convert the VOB files in the TS-Folder of the DVD back to DV which iMovie is designed to handle.
a DVD is in a compresed format called mpeg2, which is standard across all DVDs. This is what is known as a 'final delivery format' and is not suitable for editing. Because is is compressed, a 4.7GB DVD can hold a two hour movie (dual layer DVDs twice that), whereas the DV stream from a video camera, which runs at about 13GB per hour, is not compressed and IS intended for editing.
In other words you have to 'reverse engineer' the DVD back to an uncompressed format in ordfer to edit it. There is a penalty for doing this in terms of slight quality loss, but it is one you can live with.
When you have your DVD as an icon on your desktop, double-click it, and it will open to reveal a TS-Folder containing a number of various files, some called VOB. These are the constituent parts of any video DVD.
When you have downloaded and installed mpegStreamclip, and purchased and installed the Apple mpeg2 plugin, open mpegStreamclip and drag the entire TS Folder into its window. Then using the various menus available to you (just explore them and you will get the hang of it) ask it to convert to DV.
That DV file, which will be many times larger than the original TS Folder, and which can a while to create (be patient - make coffee or prune the roses!) is what you can now import into iMovie for editing etc.
When you have finished doing that, you then have to turn the project back into a DVD.
mpegStreamclip can be downloaded from here:
http://www.apple.com/downloads/macosx/video/mpegstreamclip.html
which is free, but you must also have the Apple mpeg2 plugin :
http://www.apple.com/quicktime/mpeg2/
which is a mere $20.
Another possibility is to use DVDxDV:
http://www.dvdxdv.com/NewFolderLookSite/Products/DVDxDV.overview.htm
which costs $25.
For the benefit of others who may read this thread:
Obviously the foregoing only applies to DVDs you have made yourself, or other home-made DVDs that have been given to you. It will NOT work on copy-protected commercial DVDs, which in any case would be illegal.
