Reply to broadcasting with Ustream Help!

Using the S4 on a Imac 10.6.7 with Traktor Pro 2 and want to broadcast with ustream.
My mac has the S4 selected for sound device, and so does Ustream.
What if any changes do i need to make in Traktor pro 2 because im not getting any readings in Ustream from the S4. It is playing on my monitor only. Thanks!