You're building a Vapor app to respond to SMS messages using Twilio, and here's how you can set it up with Swift Package Manager. First, install Vapor and its dependencies using the Swift Package Manager. Next, create a new Swift project and add the Vapor package to your `Package.swift` file. Then, write some Swift code to handle HTTP requests and responses. To receive text messages, you'll need to configure your Twilio account and use ngrok to make your app visible from the Internet. Finally, add an SMS route to your app to handle incoming text messages and respond with a custom message using TwiML. With this setup, you can build a Vapor app that receives and responds to text messages using Twilio.