Step 1 Enable "iCloud Backup"
You can enable the "iCloud Backup" service following these operations: Settings > iCloud > Backup.
Step 2 Backup your data
To backup information to the cloud, you have to keep your iPhone/iPad stayed connected to Wi-Fi network. If you choose "iCloud Backup", iCloud will automatically back up your information next time when it is connected to Wi-Fi. If you want to back up right now, just select "Back Up Now" and your data will be transferred to the cloud in few minutes.Once the backup finished, you can view the stored files as well as the size in the "Manage Storage".
1. Apple only offers 5GB for users to store data freely, so you have to pay if you want to enlarge the space. In addition, iCloud only keeps the latest 3 backup files for users.
2. The backup only works when Wi-Fi network is available.