I am pretty sure that feature is built into xenforo, if you click "options" and then "user registration" you can select to start a conversation with new members i believe. ive never used this feature myself, instead i have a notice set to appear only to registered users or users of a specific group
hope this helps
XenForo Requests
Registration Message
Submitted by Rem, 22-05-2016, 08:17 PM, Thread ID: 21296
Thread Closed
RE: Registration Message 01-10-2017, 07:12 AM #11
01-10-2017, 07:12 AM
#11