Hello Magister,
You don't need to do anything with the physical connections, you can configure Broadwave to use the "Stereo Mix" as a source for the Live Stream.
You can find instructions for Vista / Windows 7 here:
http://nch.invisionzone.com/index.php?showtopic=13101
If you have Windows XP, go to sounds / recording properties, and select Stereo Mix.