Steps:

1. Start your live session. 
2. Click on the three-dot menu button to find more options. 

3. From the menu list select the "start a live stream" option. 

4. A pop-up will appear that will ask you to enter the Live stream key. If you don't know how to get a live streaming key, then please follow the following link to find out your live streaming key:
Link: https://www.youtube.com/watch?v=DYsnldPtNbs&feature=emb_logo


5. Click on the start live stream button to start live streaming.