Are you talking about turning the light off on an IP camera or a USB camera? I don't think that's something you can do programatically with a USB camera. I know at least some IP camera models have that ability. Currently, our IP camera video support is still in a testing phase. Once it's stabilized, we'll be looking into other IP camera features, such as disabling the LED.
For an IP camera, you need to select the "Ethernet / Wi-Fi" tab in iCamSource. If you do that, there will be a place to enter the MJPEG URL for your camera. If you don't know the MJPEG URL for your camera, click the Help button close to the URL field. It will take you to a webpage that will help you determine the correct URL for your camera. If your camera's manufacturer is not on that page, please send an email to support@skjm.com, and we'll try to find the right MJPEG URL for you.