It sounds like you're trying to use the iPhone camera as the webcam for iCamSource. If I'm wrong on that, please let me know. Unfortunately, the iPhone can't be used as the webcam for iCamSource because Apple doesn't allow the iPhone camera to be used as a webcam when it's connected to a computer.
The only video devices that will show up in the Video Source list are USB, built-in, or Firewire webcams (not iPhone). If you don't have one of those connected to your computer, the Video Source list will be blank. If you have a webcam connected to your computer and it's not showing up in the list, please let me know the Brand/Model of the camera.