No problem! You can take the exam as many times as it takes to pass and receive a certificate. Just click the Retry button at the end of the exam. If you go back through any part of the course for review after you have failed the exam, or close the course and come back at a later time, you may see an already answered question when you make your way back to the exam.
Just keep clicking Next to make your way through your completed exam questions. Use this opportunity to review your incorrect answers as they may be on your next try. Once you get to the results page, you can click the Retry button which will reset the exam so you can try again. Once you pass, you will receive your certificate of completion.