Can’t find how to setup Apple ID for my 10 year old

You would have to create a new Apple ID in the context of family sharing. See: How to create a new Apple ID https://support.apple.com/en-us/HT204316. 

And, see these Apple documents on family sharing, particularly the third one.

Family Sharing - Apple Support

Set up Family Sharing – Apple Support

Family Sharing and Apple ID for your child - Apple Support

Kmessi10 wrote:

This is terrible. No help. Shame on you Apple

This is a user-to-user support forum, not Apple technical support. It is not live chat. Because it's an almost all volunteer effort, you will need to wait until someone who knows the answer sees your question. Sometimes that takes longer than two minutes.

See my reply above.