iCloud automatically backs up your iOS device information daily over Wi-Fi when your device is turned on, locked, and connected to a power source.
Back up automatically
On your iOS 8 device: Go to Settings > iCloud > Backup, then turn on iCloud Backup.
On your iOS 7 device: Go to Settings > iCloud > Storage & Backup, then turn on iCloud Backup.
Back up manually
On your iOS 8 device: Go to Settings > iCloud > Backup, then tap Back Up Now.
On your iOS 7 device: Go to Settings > iCloud > Storage & Backup, then tap Back Up Now.
Important: If you don’t back up your iOS device to iCloud for 180 days or more, Apple reserves the right to delete your device’s iCloud backups. For information, see iCloud Terms and Conditions.
Last Modified: Aug 26, 2015
Source: Apple PH12520