Just convert DVD to MP4, M4V or MOV supported by iTunes.
I recommend you Aiseesoft DVD Ripper.
It could easily rip DVD to MP4, H.264, AVI, MP3, WMV, WMA, FLV, MKV, MPEG-1, MPEG-2, 3GP, 3GPP, VOB, DivX, Mov, RM, RMVB, M4A, AAC, WAV, etc. with super fast DVD ripping speed and excellent image and sound quality.
It also can edit the DVD movies, such as trim a video clip, crop the movie, merge several titles or chapters into one file and so on.
Hope can help you!