If you have the webcam properly installed on your computer, ooVoo should recognize it and you should be able to use it right away. To start a video call with a friend, you simply have to go to Actions > Start a video call. If you have difficulties, try reinstalling the driver for your webcam. This can be found on the official website of the manufacturer. Also, you can find all the available options (like resolution, quality of the video, etc) regarding a video call by going to ooVoo > Settings > Video Calls.