Where to do the AdMob integration in Xcode 13?

Question

I am almost finished with my first app for the AppStore, and am trying to integrate AdMob banners in my App. The examples say to create a ViewController class, and create the banner there. I have followed the examples from AdMob, but where do I put the code so that it gets called? I have appended the example code from AdMob to this post. I have tried to put breakpoints in the code, but it does not get called.

Please excuse me if this is too trivial a question - I am rather new to this!

import GoogleMobileAds
import UIKit

class ViewController: UIViewController {

  var bannerView: GADBannerView!

  override func viewDidLoad() {
    super.viewDidLoad()
    
    // In this case, we instantiate the banner with desired ad size.
    bannerView = GADBannerView(adSize: GADAdSizeBanner)

    addBannerViewToView(bannerView)
  }

  func addBannerViewToView(_ bannerView: GADBannerView) {
    bannerView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(bannerView)
    view.addConstraints(
      [NSLayoutConstraint(item: bannerView,
                          attribute: .bottom,
                          relatedBy: .equal,
                          toItem: bottomLayoutGuide,
                          attribute: .top,
                          multiplier: 1,
                          constant: 0),
       NSLayoutConstraint(item: bannerView,
                          attribute: .centerX,
                          relatedBy: .equal,
                          toItem: view,
                          attribute: .centerX,
                          multiplier: 1,
                          constant: 0)
      ])
   }
   
}