how to rip a dvd

You can't.

Assuming it's not a protected disk, use MPEG Streamclip with the Quicktime MPEG Playback Component ($20).

Russ

If your DVD is unprotected, Handbrake would work well. If it's a protected DVD, try MakeMKV+Handbrake (use MakeMKV to decrypt and output MKV, then use Handbrake to convert MKV to MP4). Or you can just try Free DVDAid. Good luck!