Don't bother making an MP3. Youtube just doesn't accept audio files. You would have to upload it as a video, which isn't hard just tack the audio into your computers basic video editing program (windows has windows movie maker and macs have iMovie, Final Cut or Quicktime Video) and just export the project with like an image in the videos place. The file would then be in a video container that you can upload to youtube.
Here's help with that:
I'm not sure if that link will work for you, if it doesn't go to the upload page on youtube and click the encoding help link.