The answer to this depends on why you failed. If you legitimately had special circumstances, go here. If you failed because you didn't understand something about the assignment, got the answer wrong, or something similar, then the most important thing to do is rectify that problem. Ask either your tutor or the Teaching Coordinator (as a first step) for help understanding why you failed the assignment and how you might have done things differently. It is highly likely that ideas, concepts, etc. from coursework will reappear on the exam, so correcting this deficit in your understanding is critical. A good way to do this is to re-write the coursework as a study activity.