Mp3 Converting

Okay, I know. This topic has probably been posted over and over and you're all very sick of it by now, but I'm in a hurry, and I need to know how to switch the Audacity file (.aud-?) over to an mp3 because I'm planning on giving a cd of songs I've wrote and recorded for a friend of mine. Can you please explain to me how to do this? I've tried to download LAME for converting, but it hasn't helped at all. Thank you very much!
-Rachel