Click on "Live" in the lower menu bar of the app to get to the Live Video section. Now click on the camera icon or on "Start your live video". Do not panic, this will not start your video right away. It opens up the user interface and you can check again if everything is in the right light, if the camera perspective fits, if you are easily recognizable, etc. If you have prepared everything and want to go live, click on "Start your Live Video!" at the bottom of the screen. It will not be long before you have the first visitors.
To end a Live Video, click on the "X" in the upper right corner. In the next window you can confirm or stop the stream termination.