converting a file to MP3 format

could somebody help me with this?

i have a macintosh computer, and i recorded with a built-in program called 'simplesound', and saved the file to my desktop.

i just dont know how to make it as an mp3 so i can post it here. i tried uploading it just as it was, but my computer said there was an error trying to do that.

your help will be greatly appreciated [img]images/smilies/icon_mrgreen.gif[/img]