Once you've navigated to the super invitation (the page header will include "Camera-Ready Revision") scroll passed the General Info and Reply Parameters to "Child Invitations". The total count of child invitations should be in parenthesis. Listed with hyperlinks are the invitations for the papers, click on the papers you wish to revise.
List of child invitations.
On the Camera-Ready Revision page for the paper, in the General Info section there are dates listed, click the “Edit General Info” button.
Modify the expiration date to the desired point in the future and click “Save Invitation”.