How to Back up using data?

That depends on the model of your phone and the iOS version. For iOS 16 go to Settings/[your name]/iCloud/iCloud Backup. If your phone and plan are eligible there will be a switch for “Back Up Over Cellular”. Note the warning on the page under that switch, however.

You may backup your iPhone on iCloud by using cellular data if you have 5G service on your iPhone. This means that you will need an iPhone 12 or newer and active 5G service. If you do not meet this requirement, then you may not backup to iCloud using cellular data and instead use a Wi-Fi Network.

Axel F.