Hey rozlyn515,
It looks like you checked out the article about setting up Family Sharing. Let's also check out this user guide on how to set up a device for a child through Family Sharing: Set up a device for a child with Family Sharing on iPhone
1. If the child already has an Apple ID, make sure they’ve been added to the Family Sharing group. If they don’t have an Apple ID, you can create an Apple ID for them while adding them to the Family Sharing group.
2. On the new iOS or iPadOS device you want to set up for your child, press and hold the side button or top button until the Apple logo appears.
3. Bring your iPhone next to the device.
4. When you see Set Up New [device] on your iPhone, tap Continue, follow the onscreen instructions, then do one of the following:
* If you have a child in your family group, tap your child’s name.
* If you need to create a new Apple ID for your child, tap Create New Child Account, then create an Apple ID for your child.

5. Follow the onscreen instructions to finish setting up your child’s device. You can set content restrictions, communication limits, and downtime; share your child’s location with all members of the Family Sharing group, including any new members added later; and use Ask to Buy. You can change these settings at any time.
Once you've made sure you followed all the steps from this article, please try again and let us know how it goes.
Cheers!