Hello there,
You can use the code inside before head section in the template like shown in the screenshot here. Go to template options > custom code > before head and add the code.
As we know, Facebook live chat produces HTML code, so you can use our Raw HTML addon inside the pages you want to give option of live chats and insert the code there.
We don't assure the complete compatibility till now of facebook customer chat, so if there's any customization needed, you need to do it on your own for the time being.
Thanks!