How to connect your website to your Facebook Whatsapp app ?
Go to the plugin settings, and make sure to follow the instructions mentioned here :
Once done, we'll use the different values provided to setup the connection between your website and Facebook :

facebook
- API Version: Facebook API version to use in order to send Whatsapp messages, by default it's put to v16.0
- Auth Verify Token: Provide the token you will use for the verification part of the webhook, read more about it here