Hello @TeriS598 ,
You'd need to use either custom fields or tags, and upload that info to your account to update the contacts accordingly. Otherwise, you can update that info on an individual basis from within the Contacts page.
During the upload, you can make a new list of Past Due contacts, if you're just importing contacts based on that custom field info. If your import includes other Due statuses, then I'd advise using segmentation after the upload to isolate all of your Past Dues, and then send to that segment. If you included the info via tags, then you can narrow-by-tag on the scheduling page of an email.
