I have a home studio and I need to the Beat/Instrumental to play in the ATH-M20's Headphones plugged in the ATR2500 Microphone, Then I need the Beat/Instrumental AND Vocals being recorded play out of the Computer Speakers.
 
If they all makes sense to you, please reply with an solution. I am using Cakewalk SONAR X3 Producer.

If your using x3 then this is the wrong forum. And no, your post made no sense to me sorry. 
 
Far as I can tell you don't have an audio interface. You need one. Start shopping. 

Okay let me explain this better. I want the beat to play in the headphones in the recording booth then I want the live vocals to play with the beat out of my studio monitors. What kind of interface would I need my microphone is usb and the headphones plug in to the microphone.