Step 1- Go to Settings and click on Whatsapp API Number.
Step 2- Click on Add API Number.
Step 3- Click on Continue.
Step 4- 1. Click on add new API Number
2. Select existing API if you've Whatsapp Business API.
Step 5- Enter the API Number. Note: It should not have Whatsapp Account.
Step 6- Then proceed, Fill your Business Info & Whatsapp Business Profile Info.
Step 7- Give Facebook access to email@example.com to complete the process and attach the screenshot.