How can I add View in StackLayout?

I have created a simple StackLayout app and want to install the Google Mobile Ads component provided by Xamarin. How can I add the BannerView onto my app right under my hackLabel? I'm not sure how to add any type of View to a StackLayout. Any help would be greatly appreciated.

Thanks!

namespace LifeHacks
    {
        public class App : Application
        {

            const string bannerId = "ca-app-pub-XXXXXXXX";
            BannerView adView;
            bool viewOnScreen = false;

            public void AddBanner ()
            {
                // Setup your BannerView, review AdSizeCons class for more Ad sizes. 
                adView = new BannerView (size: AdSizeCons.Banner, origin: new CGPoint (-10, 0)) {
                    AdUnitID = bannerId,
                    RootViewController = this
                };

                // Wire AdReceived event to know when the Ad is ready to be displayed
                adView.AdReceived += (object sender, EventArgs e) => {
                    if (!viewOnScreen) View.AddSubview (adView);
                    viewOnScreen = true;
                };

                adView.LoadRequest (Request.GetDefaultRequest ());
            }

            static readonly StackLayout mainStackLayout = new StackLayout {
                Spacing = 0,
                VerticalOptions = LayoutOptions.FillAndExpand,
            };

            public App ()
            {

                AddTopElement ();

                var hackLabel = new Label {
                    Text = getHacks(),
                    BackgroundColor = Color.White,
                    HorizontalOptions = LayoutOptions.CenterAndExpand,
                    VerticalOptions = LayoutOptions.Center,
                    HeightRequest = 400,
                    WidthRequest = 340,
                    FontFamily = "Helvetica Neue",
                    FontAttributes = FontAttributes.Bold,
                    FontSize = 24,
                    TextColor = Color.Black,
                    XAlign = TextAlignment.Center,
                    YAlign = TextAlignment.Center,
                };

                mainStackLayout.Children.Add (hackLabel);

                var nextBtn = new Button {
                    Text = "NEXT",
                    BackgroundColor = Color.FromRgb (255, 129, 61),
                    HorizontalOptions = LayoutOptions.FillAndExpand,
                    BorderRadius = 0,
                    HeightRequest = 60,
                    FontFamily = "Helvetica Neue",
                    FontAttributes = FontAttributes.Bold,
                    FontSize = 25,
                    TextColor = Color.White,
                };


                mainStackLayout.Children.Add (nextBtn);

                var shareBtn = new Button {
                    Text = "SHARE",
                    BackgroundColor = Color.FromRgb (0, 144, 219),
                    HorizontalOptions = LayoutOptions.FillAndExpand,
                    BorderRadius = 0,
                    HeightRequest = 60,
                    FontFamily = "Helvetica Neue",
                    FontAttributes = FontAttributes.Bold,
                    FontSize = 25,
                    TextColor = Color.White,
                };

                var rateBtn = new Button {
                    Text = "RATE",
                    BackgroundColor = Color.FromRgb (164, 33, 255),
                    HorizontalOptions = LayoutOptions.FillAndExpand,
                    BorderRadius = 0,
                    HeightRequest = 60,
                    FontFamily = "Helvetica Neue",
                    FontAttributes = FontAttributes.Bold,
                    FontSize = 25,
                    TextColor = Color.White,
                };

                mainStackLayout.Children.Add (new StackLayout {
                    HeightRequest = 60,
                    Orientation = StackOrientation.Horizontal,
                    Children = 
                    {
                        shareBtn, rateBtn
                    },
                    Spacing = 0,
                });


                var bottomElement = new Label {
                    BackgroundColor = Color.FromRgb(214,34,125),
                    HeightRequest = 100,
                    WidthRequest = 340,
                };

                mainStackLayout.Children.Add (bottomElement);


                MainPage = new ContentPage {
                    Content = mainStackLayout,
                };


                shareBtn.Clicked += (sender, e) => {
                    DependencyService.Get<IGoogleAnalytics>().TrackEvent("Share", "Load", hackLabel.Text);

                    string hackLabelText = hackLabel.Text + " - See more Lifehacks and Tips https://appsto.re/us/MXRB5.i "; 

                    DependencyService.Get<INativeShare>().ShareMessage(hackLabelText);

                };

                nextBtn.Clicked += delegate {
                    hackLabel.Text = getHacks();
                    DependencyService.Get<IGoogleAnalytics>().TrackEvent("Hacks", "Next", null);
                    DependencyService.Get<IGoogleAnalytics>().TrackEvent("Hacks", "Load", hackLabel.Text);

                };

                rateBtn.Clicked += (sender, e) => {
                    DependencyService.Get<IRate>().LaunchRate();
                    DependencyService.Get<IGoogleAnalytics>().TrackEvent("Rate", "Load", null);
                };

            }

            static void AddTopElement()
            {


                mainStackLayout.Children.Add(new Label {
                    Text = "Life Hacks",
                    BackgroundColor = Color.FromRgb(107,212,101),
                    HorizontalOptions = LayoutOptions.FillAndExpand,
                    VerticalOptions = LayoutOptions.FillAndExpand,
                    HeightRequest = 58,
                    WidthRequest = 340,
                    FontFamily = "Helvetica Neue",
                    FontAttributes = FontAttributes.Bold,
                    FontSize = 46,
                    TextColor = Color.White,
                    XAlign = TextAlignment.Center,
                    YAlign = TextAlignment.Center,
                    TranslationX = 0,
                    TranslationY = 0,
                });

                mainStackLayout.Children.Add(new Label {
                    Text = "Stupid, Simple, Everyday Tips For Life",
                    BackgroundColor = Color.FromRgb(107,212,101),
                    HorizontalOptions = LayoutOptions.FillAndExpand,
                    VerticalOptions = LayoutOptions.FillAndExpand,
                    HeightRequest = 30,
                    WidthRequest = 340,
                    FontFamily = "Helvetica Neue",
                    FontAttributes = FontAttributes.None,
                    FontSize = 18,
                    TextColor = Color.White,
                    XAlign = TextAlignment.Center,
                    YAlign = TextAlignment.Start,
                    TranslationX = 0,
                    TranslationY = 0,
                });


            }

}