Did you plug the webcam into the MacBook Pro after launching the iCamSource Pro? The iCamSource Pro asks the operating system for a list of connected webcams when it starts up, so if you plug the webcam in afterwards then the iCamSource Pro won't detect it.
If you fully quit the iCamSource Pro (not by clicking the red bubble in the top-left of the window, that just hides it, but by choosing the Quit iCamSource Pro menu item after clicking the iCamSource Pro icon in the menu bar of you Mac, near the clock) and restart it then the webcam should show up in the list if it is already plugged in.
If not, you could try rebooting the Mac with the webcam still plugged in and then launch the iCamSource Pro to see if it shows up in the list. Also make sure that the webcam is plugged directly into the Mac and not into a USB hub, because sometimes that can cause issues.