Adding additional parent to child under 13 Meta Quest/Horizon account

I set up a Meta Quest account for myself and added a child under 13 account. I'm trying to add an additional parent to manage the account and/or switch the parent over the child account. I can't seem to find directions on how to do this. The only directions I have found seems to be missing a step and so I can't actually initiate the process.

Can someone explain how to do this?

Thanks.