When you first log in to the studio, a camera setting will pop up for you to adjust. You can choose which camera you would like to give access to while in the studio, including the microphone. In order to join the project room, access to the webcam & microphone is required. However, you can always hide your camera or mute your microphone once you start or before your broadcast.
Then, choose your camera in the pop-up menu.
You can add another webcam anytime with "Add another camera button".