There are two ways to set up delivery notifications. You can either blanket notify one or more people of all deliveries or you can ask that delivery personnel select their specific recipient, just like visitors select contacts.
To assign a contact to be notified for all deliveries, just like assigning contacts to other buttons, you can do so directly from the contact. Just select the contact from the Contacts tab and select Delivery under their button assignment:
Or via the Delivery Button settings:
To require delivery personnel select the specific package recipient, edit your delivery button and scroll down to the contacts section. Enable to option for 'Contact Required' then select all available delivery recipients for display on your iPad.