You can use this in the messenger channel or omni channel. 

You will need to export contact list from Manychat, and then put their API key in UChat, and then wait for the list to be imported.

Video tutorial here:
https://www.youtube.com/watch?v=AGGxo5yjeGM

Shared Docs:
https://pitch.com/public/3e27c123-fc1e-4b19-9d4f-16f2d97d0c3c