Connect your iPhone to Wi-Fi
Open Settings
Tap your name at the top
Tap iCloud
Tap iCloud Backup
Turn on Back Up This iPhone
Tap Back Up Now
Stay connected to Wi-Fi until the backup finishes
Check the last successful backup time in iCloud Backup
To back up to a Mac, connect your iPhone to your computer
Open Finder on Mac or iTunes on Windows
Select your iPhone
Choose Back up all of the data on your iPhone to this Mac or This computer
Click Back Up Now
To encrypt the backup, select Encrypt local backup and set a password