Replace the video below by clicking into it and clicking on the "Embed Options" tab on the right. You can then simply paste in the direct link to YouTube or Vimeo. Then, hide this element when you're finished!
If you would rather embed a video or stream from a different service, use the "Livestream - iFrame Block", which can be found hidden in the Layout Tab.
Need more help? Here are some great Help Center articles regarding embed best-practices: