After creating your developer app, the next step is to set up the WhatsApp API for your app. This process involves linking your own phone number, which will serve as your official WhatsApp Business account.
Immediately after creating the app, you will see the welcome screen. If your Business Portfolio is set up correctly, click Continue.
On the Quickstart tab, click Start using API, which will redirect you to the API Setup tab.
In this tab, you can add your own phone number. Meta has automatically assigned you a test number, which you can use to test the connection, but you must add your own number for production use. To add it, click Add phone number.
Fill out the form to add a phone number and create a WhatsApp Business account. Your name and description will be displayed to customers when communicating via WhatsApp.
After verifying your phone number, you will be redirected to your Business Portal (business.facebook.com) where you will create a system user to obtain a permanent access token.