To multistream to Facebook, please go to your Facebook page and click on "Live" under create post.
Next, click on "Create live video"
Next, under "Select a video source" section, please select "Streaming Software"
Now, you will find your stream key. To access your RTMP URL, please click on the "Advanced Settings" drop down menu. Please make sure that "Persistent Stream Key" is turned on and copy the stream key along with Server URL into your multistreaming source
Now, you will be able to multistream to Facebook.
Make sure to click "Go Live" on Facebook after you have verified that the multistreaming is working.