This page is practice only, and not visible on the site unless you know the URL.
First thing you should do is click the icon on the RHS above, ‘Toolbar Toggle’. This will reveal additional formatting icons.
Editting is pretty much standard wysiwyg. Add an image using the ‘Add Media’ button above. That takes you to a library of images already uploaded.
To add a Youtube or Vimeo video, go to the Youtube site where the video. Then paste the link onto the page. Simple!