I'm not getting sound into Audacity

I’m running mac os x 10.7.5 and I have dmg version 1.3 Beta. My input is Numark Mixdeck via usb and Serato. Do I have to use an audio cord as well and if I do where do I run it from record,booth,or master? And am I using the right version of Audacity. Can you please help I’m trying to record a mixtape with vocals for internet radio. I just need to know over all what to do-Thank you for your time.

Step one will be to trash Audacity 1.3.5 and install the latest 2.0.2.