hello_world.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="HelloWorld.HelloWorld">

    <StackLayout>

        <Label 
            Text="Hello World!" 
            HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand" 
            FontSize="Title"/>


    </StackLayout>

</ContentPage>