If you want to stream your pre-recorded video, and switch to the actual live in the same stream, you can follow these steps:
1. Setup your Web Cam layer.
2. Add a Microphone Layer.
3. Hide a layer with Camera and Microphone. Then add a Video Layer and start streaming (click GO LIVE button).
4. Once you're ready to switch from a Pre-recorded Video to the actual live stream, hide or remove a Video Layer. Then unhide Camera Layer as well as Microphone, and click "Sync with Live" button to make your changes visible to your audince.