Couldn't create room: Missing mandatory element (admin_key)

Hi all:

I get this error whenever I try to run the Janus Screen Sharing demo (Janus WebRTC Server (multistream): Screen Sharing Demo) (using https)

If you’re using the online demo server, it’s normal: we locked down the creation of rooms because people kept on abusing the server, and that demo needs that functionality. You can test the screensharing demo instaling your own instance of Janus.

Ok. I understand.
Thank you.