You can initiate WhatsApp notifications with templates using Node.js and Twilio's WhatsApp API. To start, you need to have a free Twilio account, a WhatsApp account associated with your phone number, and connect to the Twilio Sandbox for WhatsApp. You'll also need to design a message template that falls into one of the approved categories, such as appointment reminders or appointment updates. The template can include placeholders for dynamic content, which you can customize when sending a message. To submit a template for approval, visit the WhatsApp message template section of your Twilio Console. Once approved, you can use the Twilio Sandbox to test out your template and send notifications using Node.js. You'll need to replace placeholder values with your actual phone number and credentials stored securely in an environment variable file.