PLEASE HELP!!!!!!!!

I recently bought a "BEHRINGER XENYX X2442 USB MIXER" for my home studio which is Logic 9 based. I followed the manual to a T while hooking the mixer up to my Macbook Pro, yet I am still having problems getting Logic 9 to record any of my vocals. Since the mixer has USB capabilities, all I had to do was plug the USB cable into my macbook. My macbook recognizes the mixer, but I am unable to record any vocals into logic. I have my mic plugged into channel 1 on the mixer, and I am able to get feedback into my headphones, but when I record enable into logic I'm getting no signal. CAN SOMEONE PLEASE TELL ME WHAT I AM MISSING? I'm trying to figure out if I need to enable something on the mixer or if I need to enable something in Logic 9... SOMEONE PLEASE HELP!!!