You're right
you need to find a piece of software compatible with your system (windows, mac, linux) able to convert dvd to .divx, xvid or avi.
Make a google search with that key words, and you'll find something for sure.
Be aware that converting to divx (proprietary format) or xvid (free format) will certainly be the better choice, because it will shrink the size of the file a lot, what is a good point to put online content for downloading or streaming.