App.xaml.cs

using System.Windows;
using Cirrious.MvvmCross.ExtensionMethods;
using Cirrious.MvvmCross.Interfaces.ServiceProvider;
using Cirrious.MvvmCross.Interfaces.ViewModels;

namespace Casino.UI.Wpf
{
    public partial class App
        : Application
        , IMvxServiceConsumer
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            var start = this.GetService<IMvxStartNavigation>();
            start.Start();
        }
    }
}

MainWindow.xaml

<Window x:Class="Casino.UI.Wpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid x:Name="TheGrid">        
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;

namespace Casino.UI.Wpf
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        public void Present(FrameworkElement toShow)
        {
            TheGrid.Children.Clear();
            TheGrid.Children.Add(toShow);
        }
    }
}

Program.cs

using System;

namespace Casino.UI.Wpf
{
    public class Program
    {
        [STAThread]
        public static void Main()
        {
            var app = new App();
            var ourWindow = new MainWindow();
            var presenter = new SimplePresenter(ourWindow);
            var setup = new Setup(app.Dispatcher, presenter);
            setup.Initialize();
            app.MainWindow.Show();
            app.Run();
        }
    }
}

Setup.cs

using System.Windows.Threading;
using Cirrious.MvvmCross.Application;
using Cirrious.MvvmCross.Wpf.Interfaces;
using Cirrious.MvvmCross.Wpf.Platform;

namespace Casino.UI.Wpf
{
    public class Setup
        : MvxBaseWpfSetup
    {
        public Setup(Dispatcher dispatcher, IMvxWpfViewPresenter presenter)
            : base(dispatcher, presenter)
        {
        }

        protected override MvxApplication CreateApp()
        {
            return new Core.App();
        }

        protected override void InitializeDefaultTextSerializer()
        {
            Cirrious.MvvmCross.Plugins.Json.PluginLoader.Instance.EnsureLoaded(true);
        }
    }
}

SimplePresenter.cs

using System.Windows;
using Cirrious.MvvmCross.Wpf.Views;

namespace Casino.UI.Wpf
{
    public class SimplePresenter : MvxWpfViewPresenter
    {
        private readonly MainWindow _mainWindow;

        public SimplePresenter(MainWindow mainWindow)
        {
            _mainWindow = mainWindow;
        }

        public override void Present(FrameworkElement frameworkElement)
        {
            _mainWindow.Present(frameworkElement);
        }
    }
}