Plex setup on Synology to control through Alexa

[Jerome]

Hi,
I installed the brand new Plex skill on my Amazon Alexa.
https://www.plex.tv/alexa/

Then I installed the Plex package on my Synology DS212, launched Plex on the Syno and scanned movies and music stored on the Syno.
When I say "Open Plex" then "Play something to listen to", Alexa replies :
"You have not selected a Plex player to use. Would you like to do that now ?"
I answer "Yes"
Alexa : "I could not find any Plex companion players on your network.
Please make sure your player is running and connected to the internet."

What's that Plex companion player ? How do I enable it on my Synology ?
I am missing a piece here 
Thanks for your advice.

Jerome

[mike27oct]

Feb 2 email from Plex News tells of how they are integrating Alexa into Plex.  Maybe you got this email, too.