It's quite easy really. Linux Mint comes with everything you need to do this.
1. Insert the CD you want to rip.
2. The Rhythmbox 0.11.5 should open up.
3. Click on EDIT then PREFERENCES and click on the MUSIC tab.
4. Be sure that the Prefered format is set to MP3 or whatever format you want. And also the Library Location is where you want it. Example /home/drake/Music
5. Click Close and you should be back in the Rhythmbox interface. Click COPY TO LIBRARY
There you go.