mp3 files content tags that can hold various information about the title of the song, author, year, genre, comments. It is useful to edit this information to get your files organized. This tip sheet will tell you how to do it in iTunes and Audacity.
If you just recorded your file in Audacity or you opened a WAV or AIF file and you want to export it to an mp3 file, follow our Converting Audio File Formats - wav or aif to mp3 tutorial. If you want to change the metadata for an existing file, you may use iTunes (see above).