iMOVIE don’t support DVD, you can convert your dvd files to mov or mp4. There are many tools you can use, I alwasys use Adoreshare Video to iMovie Converter from http://adoreshare.com/products/video-to-imovie-converter-for-mac.html
This program is powerful, I often use it to convert to 1080P videos. You can have a try
HOW DO I SEND A DVD RECORDED ON A BROKSONIC DVD RECORDER INTO iMOVIE? The when I copy the DVD onto my desktop the individual folders have units of the DVD info as Unix executable files. I don’t know what I’m doing. HELP!!!