OS X El Capitan: Set up iCloud on your Mac
To use iCloud on your Mac, you need to sign in to iCloud using your existing Apple ID, or a new one, then select the iCloud features you want to use.

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Choose Apple menu > System Preferences, then click iCloud.
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Enter your Apple ID, then follow the onscreen instructions.
Important: Be sure to use the same Apple ID for iCloud on all your devices.If you want to use one Apple ID for iCloud and a different Apple ID for the iTunes Store, App Store, and iBooks Store, be sure that you enter the Apple ID you want to use for iCloud here. For more information, see the Apple Support article Sign in with your Apple ID on a new device.
If your Apple ID uses two-factor authentication, you’re asked to authorize this Mac to use your iCloud account by entering the passcode of an iOS device or a Mac you set up for iCloud.
To set up iCloud on your iOS device, Apple TV, or Windows computer, follow the instructions on the How to set up iCloud website.