You can only cancel a submission within the first 10 minutes of submission, and only if it has not been assigned to a project reviewer yet. Once a project has been picked up for review you will not have the option to cancel your submission.
If you would like to cancel your submission for a project you will first want to navigate to the project page in the classroom. Once there you will see a link to Cancel Submission in the upper right-hand corner of the page:
Click on this link will bring up a pop up asking you to confirm the cancellation of your project:
Once you click “YES, DELETE MY SUBMISSION” your submission will be cancelled. You will receive a notification at the bottom confirming it has been cancelled:
Once your project submission has been successfully cancelled you will see the option to resubmit your project at the bottom of the page: