The importing procedure is same as importing attendee database in EventX.
A few important points need to take note when importing secondary email(s) with your attendee database:
1) All cc emails should be placed in one single column.
2) If there are more than one CC email, all emails need to be separated by a comma without space in between.
3) By default, column that contain emails will be mapped to "Primary Email" column.
4) Remeber to map the column of CC emails to "Secondary Email(s)" column in the EMS plaftform.
5) You can find the imported Secondary Email(s) in the attendee list.
6) You can also view/edit/add the Secondary Email(s) in the attendee's detail page.
Related article: Import attendees into EventX