How do I Back up to family shared iCloud
Looking to access my shared family drive
iPhone 8 Plus, iOS 16
Question marked as
You backup to shared iCloud storage the same way that you would if you weren't using shared storage. See instructions in How to back up your iPhone or iPad with iCloud - Apple Support
With shared storage you continue to use your own Apple ID and access the storage in the same way as you would if you weren't sharing. The only thing that changes is the amount of storage available and the billing. See information in Share iCloud+ with your family - Apple Support