Step 1: Connect iPhone to computer and open iTunes to back up to computer.
Step 2: Enable iCloud Backup in Settings > [your name] > iCloud > iCloud Backup.
Step 3: Check that important photos also backup to iCloud Photos.
Step 4: iCloud backups happen automatically when connected to WiFi and power.
Step 5: View latest backups under Settings > [your name] > iCloud > Manage Storage > Backups.