If the Challenge stage is open, you can always delete your Submission and try again. Doing so, however, may delete all feedback and rubric results associated with your first Submission.
There is functionality that allows you to delete a Submission and resubmit, however your Exercise must be configured to allow this by your Instructor. If your Exercise has this configuration, you can follow these steps to resubmit:
Visit the Challenge stage. Under your Submission select the red Retry Submission button.
Click on “Retry Submission” and a popup will appear on your screen saying: Are you sure you want to archive this Submission and retry this Exercise?
Select OK and then record your submission again.
To view your prior attempts, select the View your prior attempts link.
This will take you to a page with a list of all your past Submissions and links to each archived Submission page to view the details of each Submission.