You can add your Facebook messenger to your map by filling in the Messenger field in your user interface at the end of the url of your messenger link.

For example:

In the case of our full Messenger link: https://www.messenger.com/t/card.pm

Keep only the end of the link, i.e. "card.pm" in the Messenger field, then save.

How do I find my Messenger URL? Click on the Contact button on your FB page > A small window will open > Go to the window settings then click on open in Messenger > You will see the url of your Facebook Messenger in the address field of your browser.