Expiring document notifications are set up to send a notification to the user assigned to the background checks in Access Screening:
This is set at Brand level where notify Users of expiring documents has been selected.
If you wish to change this you need to reassign the Background checks to a different User.
Each of your users need to set up their email notifications by selecting Configuration in the left menu on Access Screening then selecting email notifications - this is not something we do for you.
Each User needs to subscribe to the email notifications how they wish to receive their emails and when.