To save Whatsapp number in a QR Code, follow the steps given below:
Login to your account
Select Social Media Links QR Code from recommended category
When you scroll down, you'll find 'Whatsapp' button in add section. Click on it
Enter your whatsapp number
Click on create QR Code
A window will appear prompting you to name and save the QR Code. Click on save
You can then proceed to customize and download your QR Code