Sign in as the family manager and go to Settings > Parental Controls/Family Management > Family Management.
Select an adult family member and enable Parent/Guardian.
How to upgrade a child account to an adult account
When a child is eligible to upgrade to an adult account, they see a notification when signing in to PSN. They can then choose to follow the on-screen instructions to upgrade to an adult member or select Do This Later.
Upgrading the account isn’t required.
You can’t revert to a child account once upgraded.
To upgrade after selecting Do This Later, follow the steps below: