I did this in the MainActivity.cs as it suggested.
using System;
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Xamarin.Forms.Platform.Android;
namespace SalesnetRest.Droid
{
/// <summary>
/// Main Class
/// </summary>
[assembly: Xamarin.Forms.ExportRenderer(typeof(Telerik.XamarinForms.Input.RadCalendar), typeof(Telerik.XamarinForms.InputRenderer.Android.CalendarRenderer))]
[Activity (Label = "Salesnet CRM", Icon = "@drawable/Icon", MainLauncher = false, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation,Theme = "@style/AppTheme",ScreenOrientation=ScreenOrientation.FullSensor)]
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsApplicationActivity