Need info/help with internal/external sound mixer...

Calling Mac heads and Music heads!
Nothing too big..just need some specific and easy info on how to do something.

I am going to be using ustream to broadcast a radio station {seeing in how ustream is free}. I read this article: http://www.associatedcontent.com/article/2055197/step_by_step_instructions_on_starting.html?cat=3 - which states step-by-step what to do to create and get the ball rolling on such a project, but the guy is using a PC. Ugh. Gross.

I currently have a Numark NS7 Dj Turntable system and thought maybe I could hook that up and make it work as a mixer of sorts, but I tested that idea and it did not seem to work out how I thought. Anyone know if I am going to need to buy an external mixer? Is there a Mac program I can download? Any info would help.

Thanks in advance!