To make a child account an adult account, sign in to Xbox Live using the account you want to change. After you reach adulthood (which varies by country and region), you can convert a child account to an adult account. If you entered an incorrect date of birth when you created the account, you can only create a new account with the correct date of birth. IIRC, you either can’t advertise it and have to wait until the age of the account’s user turns 18, or you’ll have to play around in adult account settings.
Note: This option is only available if the account’s date of birth indicates that you have reached adulthood (18 years in the UK).
How do I change my Xbox account to 18+?
If you’re a parent editing your child’s age, go to the My Family section of your account to make changes to an account that isn’t your own. Account holders younger than 18 years of age receive child accounts in the United States and the UK. Select Family Settings and select Manage family members to view the list of accounts for your device. This type of account is monitored by a Windows Live ID to restrict family settings, and some features are limited.
Xbox LIVE determines whether an account is a child or an adult account, based on the age of the account holder.
How can I switch my child account to a normal account?
The steps above will help you easily make changes and manage a child’s account. These are also accessible via mobile devices if your child is signed in to their Gmail account. To proceed with changing a child account to a parent’s account, you can simply change the user’s age and also the name. If your child has ideas for projects that could involve holding (such as a class scavenger hunt), they’ll need to share their content with specific people when they create the note.
the various options that appear in front of you, tap Manage Settings so you can make changes.