how do submit information about the deceased person

You need to get a Court Order, so it's to the Court that you submit the various details of the person - they will advise you what they need. The article linked to at the top of this page specifies what is neeeded by Apple and gives you a link to contact them once you have the Court Order.

This is primarily a user-to-user support forum; other Apple users like you. Contact Apple Support. See the following from How to request access to a deceased family member's Apple accounts - Apple Support

If you have a court order with this information, or if you need additional help, please contact Apple Support.