Setting up your calendar sync can be useful in many ways, and it is easy. To get started go to "Set Up" > "Calendar Sync" and click on "Activate calendar sync".
Now follow the steps on the screen to connect your iCal, Exchange, Office 365, Outlook.com or Google Calendar.
As soon as you connected the first calendar, you can also connect further calendars you want to sync with. This can be done via the "Activate calendar sync for more calendar providers" button.