How to set up e-mail groups

This may help: https://support.apple.com/guide/contacts/email-a-group-or-smart-group-adrb475c5d8d/mac

It would help us if you told us what email/address app you are using. If you are using Apple's Mail, it works with Apple's Contacts app, which is where groups are created. Instructions for doing so are easy to do and the steps to do so are in the Contacts Help information.