Ionic3 Push notification with firebase

Hello, I'm trying to use the ionic push plug in, with firebase but he's asking me to do something. but I can not find and solve it.

import UIKit
import Firebase

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

  var window: UIWindow?

  func application(_ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?)
    -> Bool {
    FirebaseApp.configure()
    return true
  }

I have xcode on my mac