You need to enable the live chat option from the dashboard. To enable that, log in to your dashboard and go to Integrations, click on the connect button under the Live Chat option.
Enable the Live Chat option and select Whatsapp. Add your Whatsapp number and write a message that will be shown to the customers-
Save changes after you are done.
This is how it will look in the frontend for the customers-
This is how you can integrate WhatsApp with your eCommerce store.