To set up another contact to receive notifications of all expirations, go to their Contact profile and select the ‘Notification Settings’ Tab (1), check all that you want to apply in the section under Watched Expiration Item Notifications (2) and then Update Notification Settings (3) before proceeding to setting up which expiration items you want the contact to watch by clicking on ‘expiration items you’re watching’ (4).
When you are redirected to the following page, you can choose to have the contact watch all expirations by clicking on the green button. If you would like them to watch only a certain group of expiration items, you can set up a rule by selecting ‘Edit Rule’ and for example have the Contact watch only items that they are an Owner to, or have them watch items of certain categories. Save the rule for the condition to apply.
Keep in mind that the contact will not show up as a contact to notify when you view the expiration item's profile.