Privacy
The first thing you'll notice when you get connected is that Flash will ask you if it may have access to yout camera and microphone. Select allow if you're going to be hosting or participating in the presentation as a live audience member. You can select "Deny" if you only want to watch.
Microphone
Make sure your microphone is connected. Click on the microphone tab to bring it to the front. Select your audio source from the drop-down menu. If you have a FireWire camera with a built in microphone, only Macs will be able to utilize it over the webcast system. PCs will have to use another source. You'll see the meter move up and down if Flash was able to detect your camera. You can boost your recording level by adjusting the "Record Volume" slider. Enable "Reduce Echo" if you're listening to the webcast over speakers instead of headphones.
Camera
Make sure that your camera is properly connected and the correct drivers are installed if necessary. Select your camera from the drop-down menu and click the blue box with the webcam icon in it. If Flash is able to detect your camera, a preview of your camera feed should come up. If it doesn't, you might have to refresh the webcast page and try again.