Download M-peg Streamclip converter.
Purchase and download Quicktime M-peg 2 playback.
The Squared5 website should have instructions all over it for converting video and audio files from many sources, including DVDs, to various formats, like Quicktime Movie files.
Following the instructions, you would import the relevant video and/or audio files from the DVD disc into the Streamclip converter, choose the format you wish to output to – which in this case would be Quicktime Movie – and start the conversion process. When it’s done you will have a Quicktime Movie file of the DVD video which is obviously compatible with Final Cut.