Set up iCloud on all your devices. The rest is automatic.

To get the most out of iCloud, update to the latest system requirements.
Then set up your iPhone, iPad, iPod touch, Mac, and PC.

iCloud requires iOS 5 or later on iPhone 3Gs or later, iPod touch (3rd generation or later), iPad, or iPad mini; a Mac computer with OS X Lion v10.7.5 or later; or a PC with Windows 7 or Windows 8 (Outlook 2007 or later or an up-to-date browser is required for accessing email, contacts, and calendars). Some features require iOS 7 and OS X Mavericks. Some features require a Wi-Fi connection. Some features are not available in all countries. Access to some services is limited to 10 devices.