Back up iPhone 12

These are the generic instructions:--> How to back up your iPhone or iPad with iCloud

Also, take a look at the section "Find and manage backups stored in iCloud" in this support article:--> Locate backups of your iPhone, iPad, and iPod touch

Regards

Giulio

Back up iPhone using iCloud

Go to Settings > [your name] > iCloud > iCloud Backup.Turn on iCloud Backup.

iCloud automatically backs up your iPhone daily when iPhone is connected to power, locked, and connected to Wi-Fi.

Note: On models that support 5G, your carrier may give you the option to back up iPhone using your cellular network. Go to Settings > [your name] > iCloud > iCloud Backup, the turn on or off Backup Over Cellular.