There is no need to withdraw your application at this point.
On first iteration Match Day, the first iteration match results will be published. Shortly after, you will be able to see what positions are available for the second iteration on the program descriptions page on carms.ca.
From the opening of second iteration until file review, you will be able to make changes to your application, assign documents and apply to programs in CaRMS Online. All documents should be assigned to second iteration programs before the beginning of file review. Consult the second iteration timeline for exact dates.