Set up iCloud Keychain on iPhone
Use iCloud Keychain to keep your website and app passwords, credit card information, Wi-Fi network information, and other account information up to date across all of your approved devices (iOS 7 or later) and Mac computers (OS X 10.9 or later). iCloud Keychain is secured with 256-bit AES encryption during storage and transmission, and its data cannot be read by Apple.
iCloud Keychain can also keep the accounts you use in Mail, Contacts, Calendar, and Messages up to date across all of your iOS devices and Mac computers.
Set up iCloud Keychain
If you didn’t turn on iCloud Keychain when you first set up your iPhone, go to Settings > [your name] > iCloud > Keychain, turn on iCloud Keychain, then follow the onscreen instructions.
When you set up iCloud Keychain, you create an iCloud Security Code, which you can use to authorize additional devices that use your iCloud Keychain. It’s also used for verification so that you can perform other iCloud Keychain actions, such as recovering your iCloud Keychain if you lose all your devices.
Set up iCloud Keychain on an additional device
When you turn on iCloud Keychain on an additional device, your other devices using iCloud Keychain receive a notification requesting your approval of the additional device.
On one of your other devices, approve the additional device. Your iCloud Keychain automatically begins updating on the additional device.
To approve iCloud Keychain when you don’t have access to your other devices, follow the onscreen instructions to use your iCloud Security Code.
Reset or create an iCloud Security Code
If you enter the wrong iCloud Security Code too many times when using iCloud Keychain, your iCloud Keychain is disabled on that device, and your keychain in iCloud is deleted.
To reset or create a new iCloud Security Code, see the Apple Support article If you enter your iCloud Security Code incorrectly too many times.
To learn more about iCloud Keychain, see the Apple Support article Set up iCloud Keychain.