Change iCloud Storage preferences in Family Sharing on Mac
On your Mac, use iCloud Storage preferences in Family Sharing to upgrade your iCloud storage and share it with family members.
To change these preferences, choose Apple menu > System Preferences, click Family Sharing, then select iCloud Storage in the sidebar.
You can change the amount of iCloud storage that is shared among the Family Sharing group. Click Upgrade to see your current iCloud storage plan and the other plans and monthly prices that you can choose.