To enable iCloud on your Windows PC (Windows 7 or 8 required), first set up iCloud on your other devices, then install the iCloud Control Panel for Windows.
Open the iCloud Control Panel and enter the Apple ID you used to create your iCloud account. Select the iCloud services you’d like to enable and click Apply.
To enable automatic downloads for your music, apps and books, open iTunes > Edit > Preferences > Store and select Music, Apps and Books.*
*Automatic downloads and downloading previous purchases require iOS 4.3.3 or later on iPhone 3GS or later, iPod touch (3rd generation or later), iPad or iPad mini; iOS 5 or later on iPhone 4 (CDMA model); or a Mac or PC with iTunes 10.3.1 or later. Previous purchases may be unavailable if they are no longer in the iTunes Store, App Store or iBooks Store. Downloading previous movie purchases requires iTunes 10.6 or later, iOS 5 or later, or Apple TV software 4.3 or later. Not all previously purchased movies are available for downloading to your other devices. Download iTunes free.
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.