How to set a custom greeting on Facebook Messenger?

You can create a customized greeting from your FB page that will appear in Facebook chat and in Messenger app, when someone begins a conversation with your page for the first time. The greeting will appear before any messages are sent to the page.

To create a Messenger greeting:

-Click Settings at the top of your page
-Click Messaging in the left column
-Scroll to find 'Show a Messenger Greeting' and click to select Yes
-Hit the Change button to personalize the greeting and then save.