This is a Lightstream Labs feature. For info on enabling Labs features please visit this article
To add a Video File, click the plus button to add a new layer and select the Video Clip option. You will then be prompted to upload a Video File to be used on your stream. The Video File you choose must be smaller than 200 mb in size and it must be in either MPEG4 or WebM format.
Currently we do not have any controls for video playback and it will autoplay when the scene is switched to, but you have the ability to loop, stop, or hide the video. When you go live, the video will rewind to the beginning. Additionally, it will start from the beginning when you switch to that scene.
There is currently no limit to the amount of videos you can upload, but you cannot currently delete videos that you upload to a project.