As an integration between two different providers, in this topic I'm going to explain how to successfully onboard a new WABA (WhatsApp for Business Application) account;
Let's start first with understanding what is WhatsApp for Business Application:

WhatsApp Business API is a tool that allows businesses to integrate WhatsApp messaging into their customer communication platforms. It enables companies to send messages, notifications, and support responses at scale through WhatsApp

TL;DR: It's WhatsApp but with APIs.

This guide contains a step-by-step procedure that BeCloud’s Agents must follow to obtain the integration between the Agent Desktop and WhatsApp for Business.
Warnings before reading:

• The “Provider” mentioned many times in this guide was Vonage as of June 2023, so each example uses the Vonage environment and methods;

Some requirements must be met by the customer before starting the integration:

1. Meta verified Business Account and Business Manager;
2. A number that can be reachable from the USA/UK;
3. *Access to the customer Meta Business account and being a Facebook Administrator;
4. Verified Facebook Account

*Keep in mind that, to create more than two WhatsApp channels, it is necessary to be an admin of the Facebook Meta page of the company that required the service. Because Meta (Facebook) requires a verified Business to create more than two channels and two numbers.

If the requirements are met, a BeCloud Agent must send the customer a checklist that contains the sum of information that a BeCloud Agent will overwrite on the provider’s WABA form activation and (if needed) also the WABA form activation for multiple numbers.

After some days, the customer will receive a request for the “Jewel” (for Vonage) on their Meta Business account on the notification panel, which must be accepted.
Then you must proceed with requesting a new API Key where you can reside the WhatsApp Application, in order to do so, login in the dashboard > API setting and request a new API Key. After obtaining a new API Key, in the same setting tab give a name to your key and obtain an API Secret, this one will be used to link your server to your Vonage WABA Application.

After this set-up, proceed with creating a new Application. The most relevant field is “Message” in which you have to declare the webhooks. Then, go to the “External Accounts” and proceed with the Meta/Facebook wizard to link your WABA to your Vonage API Key. In this documentation I've provided more info on how to create a new WABA server and how to procceed as well.

If the requirements are met, a BeCloud Agent must send the customer a checklist that contains the sum of information BeCloud Agent will overwrite on the provider’s WABA Form Activation, after having the form compiled, proceed with contacting your Infobip Account Manager that will enable you the “Login with Facebook” button under the Channel section.
A more detailed documentation is available here.

About this specific point of the documentation, I've already prepared a documentation on the following link.