When a round of review is complete for an existing approval, you can route a further round if changes and re-review are required. To do this, load the Tracker project that your original review file is associated with. Select the Approval you would like to revise by clicking on it (you will see the row color change), which will enable the Create Revision button.
Clicking Create Revision will take you to the same screen as when you first create an approval, but you will now be in a subsequent round of review.