Using CallBackURL with Swifter on macOS

Question

I am trying to learn how to use Swifter for a macOS/iOS app, however the documentation on the site assumes a lot of knowledge I do not have.

If am building a new app, and I have my Twitter API keys from Twitter, how do I setup the callbackURL so that a user can tweet from my app? My code currently is very simple:

if (meetingSetup.twitterEnabled == true) {
    let twitterMessage = "Appropriate text"
       delegate.swifter?.postTweet(status: twitterMessage, success: { status in
       print("Twitter message: \(twitterMessage)")
    },failure: { error in
       print("Twitter message: failed")
   })
}

I then have Twitter setup in the AppDelegate as follows:

 @nonobjc func application(_ application: NSApplication, didFinishLaunchingWithOptions launchOptions: [AnyHashable: Any]?)-> Bool{
        swifter = Swifter(consumerKey: twitterConsumerKey, consumerSecret: twitterConsumerSecret, appOnly: true)
        return true
 }

However, the code doesn't actually ever post the tweet. Reading online I saw that I need a callbackURL defined, but I don't see any details on how to define this in my code, so that I can setup it up in my Twitter API configuration.

What is the appropriate way of using Swifter and callbackURLs?