At the top of the chatroom screen is a red button "Camera" Click on this and it will open your camera and you will see it in your chat window. You can drag your camera to a more convenient place.
You then get the option to make your AV stream public or private. Most people tend to make their webcam Private which means if someone wants to view you, you will get a request pop up in the main chat window. Don't Forget if there are other people with you who don't wish to appear on camera, or if you have Minors with you, Don't switch it on!