This tutorial explains how to extend a Node.js and Express app that sends notifications when a Twitch stream goes live to send notifications to multiple destinations using Courier's Lists API. The process involves creating a list of recipients, subscribing them to the list, and updating the code to use a List send instead of a regular send. Additionally, the tutorial shows how to add Discord as a notification destination by configuring the Discord integration in Courier and designing a Discord notification. Finally, the tutorial provides a full application code example that processes stream.online events and passes them to Courier along with additional stream data, creating SMS or Discord notifications based on the profiles in the list of subscribers.