@Steve143 No, I am completely wrong. In fact we are both wrong. Airbnb apparently no longer offer this feature, please see end of message and link.
This is what I get, it leads nowhere of any help.
Re: FB - I did see this post on how to write a reference (link below) and it does say you need to have a linked FB account.
https://community.withairbnb.com/t5/Tips-Tutorials/References-A-Community-Help-Guide-UPDATE/m-p/4143...
But, reading further down the post in link there is a reply saying:
@Sandra1443
Dated 09-20-2018 04:18 AM from Linda: "Apparently, Airbnb do no offer this as a feature anymore - Straight from the horse's mouth
We appreciate you reaching out to us regarding this. This is a feature we no longer offer, we apologize for the inconvenience. If there's anything else you needed, we're happy to help. "
A dead end, a waste of time. Beyond me why Airbnb don't delete the page if it is not longer applicable or at least leave a message saying "No Longer Available" would save time and confusion and linking one's FB: sharing more personal information and all one's contacts with Airbnb.