To build a conference line with Twilio and Node.js, you'll need to set up an Express server to receive incoming calls, install the necessary libraries, and configure your Twilio account to make your number publicly accessible. You can then use ngrok to provide a publicly accessible URL for your Express app, allowing it to be visible from the internet and receive requests from Twilio. Once you've completed these steps, you'll be able to join conference calls using a unique PIN or log-in, making it easy to connect with others over the phone.