To start an Activity, follow these steps.

1. Create a new Xamarin.Android application. The project template will create a single activity named MainActivity (MainActivity.cs), which contains a button.
2. Add a second activity class named Activity2 to the project. This class must inherit from Android.App.Activity
3. From the button.Click handler in MainActivity.cs, call StartActivity , passing the type of the activity to start, Activity2 in this case.

button.Click += delegate {
       StartActivity(typeof(Activity2));
};

Each screen in an application is represented by an activity. For more information on activities see the Getting Started series and the Activity Lifecycle in the Xamarin.Android documentation.