Hello AGMA,
Congrats on your first post in the Community. QuickBooks is designed to help you streamline your accounting using the powerful features offered in the program. I'll be happy to share more info so you're on the right path with achieving your goals.
To make sure we're both on the same page, are you looking to add the child as a user on the account? If so, I encourage you to check out the following article that shows you how to: Add and manage users in QuickBooks Online.
Let me know if this info helps you achieve your goal. Otherwise, you're more than welcome to reach back to me in the comments below. I've got your back.
