Sometimes the quickest, fastest way out of the box is to simply save the song to a wav file and use a 3rd party convertor, if you don't see MP3 as an option in your choices right away.

Something as simple as iTunes or LAME Front End works fine. Or Audacity.
Just be careful where you get Audacity for the next couple weeks if you decide to download it. They've had a few servers compromised recently.

I do not work here, but the benefits are still awesome
Make your sound your own!