Follow below Steps to verify a business in Whatsapp and fetch the API key:
Step 1 : Add your email and fill up your details.
Step 2 : After filling up your details click on Continue with Facebook
Step 3 : After filling up your details click on Continue with Facebook
Step 4 : Click on Get Started
Step 5 : Click on Continue
Step 6 : Choose Click on Continue
Step 7 : You can create your own business account or choose an existing one.
Step 8 : Now click on continue to Step 2
Step 9 : Now click on the Continue button.
Step 10 : Select your category and give a brief description of your business.
Step 11 : Verify your WhatsApp Business number.
Step 12 : The Last step is to add the 6 digit verification code received on your phone.
Step 13 : After adding your code, click on verify
Step 14 : Now click on OK
Step 15 : Your number is now verified, Click on Generate API key
Step 16 : Copy your API key and address paste in a secure place. Tick the checkbox and click on continue.
Step 17 : Congratulations, you have successfully verified your number.