1. Add the following statement to your code
using Microsoft.Phone.Tasks;
2. Add the following code to your application wherever you need it, such as in a button click event. To test this procedure, you can put the code in the page constructor. This is the code to launch the task.
SaveAppointmentTask saveAppointmentTask = new SaveAppointmentTask();
saveAppointmentTask.StartTime = DateTime.Now.AddHours(2);
saveAppointmentTask.EndTime = DateTime.Now.AddHours(3);
saveAppointmentTask.Subject = "Appointment subject";
saveAppointmentTask.Location = "Appointment location";
saveAppointmentTask.Details = "Appointment details";
saveAppointmentTask.IsAllDayEvent = false;
saveAppointmentTask.Reminder = Reminder.FifteenMinutes;
saveAppointmentTask.AppointmentStatus = Microsoft.Phone.UserData.AppointmentStatus.Busy;
saveAppointmentTask.Show();