Apple Logic Pro /LogicExpress Discussion

I'm probably doing something wrong, but I just
finished my first ever audio (not Midi) song, and I
want to take the 8 or so tracks I have and create a
Stereo mp3 or wav. 

I ASSUMED that the Digital Mixdown command did this.

Need-less-to-say, I got an error, which can be seen
at:

www.graphic-effects.com\error

Any suggestions on how this seemingly simple task is
done?

Thanks in advanced!

Windows, Logic Platinum 5.5.1