Make sure your Mac is running OS X v10.7.4 or later.
If you don’t have the latest version of OS X, you can purchase it from the Mac App Store.
To get the most out of iCloud on your Mac, install OS X Mountain Lion (v10.8).
Turn on iCloud.
Choose System Preferences from the Apple menu on your Mac. Click iCloud, enter your Apple ID and select the services you’d like to enable.
Want to use a different Apple ID for iTunes? Learn more
Enable Photo Stream in iPhoto or Aperture.
Open iPhoto ’11 (version 9.2 or later) or Aperture (version 3.2 or later) and click the Photo Stream icon in the left column. Then click Turn On Photo Stream. Shared Photo Streams require iPhoto 9.4, Aperture 3.4, and OS X v 10.8.2 or later.
Enable automatic downloads in iTunes.
To enable automatic downloads for your music, apps and books, open iTunes and choose Preferences. Then click Store and select Music, Apps and Books.* (Requires iTunes 10.5 or later.)
Turn on iCloud for the rest of your devices.
To get the most out of iCloud, set it up everywhere.