Exporting Audio
From Help Wiki
Audacity can export to multiple formats such as wav, mp3 or ogg. They are listed under File, Export. If you want to export as mp3 you need to download the LAME mp3 encoder. You can edit the bitrate, samplerate, etc. of the exported files under Edit, Preferences and under the Quality and File Formats tabs.
You can find instructions for downloading and installing the LAME mp3 encoder here:
http://audacity.sourceforge.net/help/faq?s=install&i=lame-mp3
