What is iCloud Keychain?

iCloud Keychain is Apple’s attempt to make a basic level of password management available to the mainstream. With it, your account names, passwords, and credit cards numbers can be stored in iCloud, and synced across all iOS 7 and OS OS X Mavericks devices that are logged in under the same Apple ID.

iCloud Keychain can also keep the accounts you use in Mail, Contacts, Calendar, and Messages up to date across all of your Mac computers. If you sign in to Facebook, Twitter, Linked In, or any other accounts in Internet Accounts on OS X Mavericks, iCloud can push those accounts to your Mac computers as well.

How do I set up iCloud Keychain?

After upgrading to iOS 7.0.3 or later, the iOS setup assistant will ask you to set up iCloud Keychain. If you skipped this step and want to set up iCloud Keychain now, follow these steps:
Use these steps if you’re using iOS 7.0.3 or later:
Tap Settings > iCloud and turn Keychain on.
Follow the onscreen instructions.
Use these steps if you’re using OS X Mavericks v10.9 or later:
Choose Apple () menu > System Preferences, then click iCloud.
Select Keychain. If you want to, you can set a passcode to unlock your screen after sleep or after the screen saver begins.
Enter your Apple ID and password.
Follow the onscreen instructions.