To send or schedule broadcast campaign, it is required to have WhatsApp Business API and a whatsapp message template appoved.
If you do not have both or any of them, follow the links given below,

1. Apply for WhatsApp Business API
2. Create and Submit whatsapp message template

Once you have API & templates ready, you can start sending automated WhatsApp messages.

As shown in the screenshot below,

1. Navigate to "Automations" menu in our application.
2. Find Order Shipped / Fulfilment section & Choose the template
3. Click "Enable"
   

   That's it. 😊

Now app will start sending automated WhatsApp messages for order fulfilment / order tracking events on your shopify store.