Directing PC audio sound to USB DAC via USB port

This is a very basic question and probably it has been discussed many times, but I have not found it. So, I ask here.
I have an Emm Labs DAC2 and trying to use the USB port. I have installed the USB driver provided by Emm labs. I connected the USB port of DAC2 to my Vista powered laptop via USB cable. The Laptop indicates the device is ready to be used. But when I open the sound device page via the control panel, I only see one sound device listed which is the default Realtek device came with the laptop. I dont see any 2nd sound device. How do I direct my audio sound to the DAC2 ? Anybody used the DAC2 for PC audio via the USB port ? I am sure there is something very simple I am missing. So, any help will be greatly appreciated.