Being an habitual user of App Inventor, switching between screens is ridiculously simple ! In Xamarin also it is … once you understand it

Layouts

The layout file is an .axml file. You can fill it up by the designer via toolbox or directly by editing source. However, the layout file is not mandatory as elements can be added programmatically

How to bind layout to activity

A layout and MainActivity.cs file is already created on project creation. It is binded by

SetContentView(Resource.Layout.Main);

for a .axml file called Main.axml found under Resources > Layout

Create new activity and layout

Right Click on project name (like App1) > Add > New Item > Activity and edit name

Right Click on Layout folder > add > New Item > Layout

in Activity1.cs bind to layout

SetContentView(Resource.Layout.Layout1);

in Main.cs

SetContentView(Resource.Layout.Main);
Button button = FindViewById<Button>(Resource.Id.button1); //button added via designer
button.Click += delegate
{
StartActivity(typeof(Activity1));
};

simple !