In order to get a Certificate of Accomplishment and Certificate Supplement you are required to pass an exam at the end of the course. Whether a course offers an exam or not, will be published on the course cover page and in the announcements from the course instructor. If that's the case you can upgrade to the Certificate of Accomplishment for the offered price.
The exam could either be an online proctored exam or a graded course project. For further information about the assessments modes, you can click here.
Once the grading is done you can download the Certificate of Accomplishment and Certificate Supplement in the "Certificate" section in the navigation bar inside the course. If you fail or miss the assessment it is not possible to get a Certificate of Accomplishment and Certificate Supplement. Unfortunately it is not possible to get a refund if you fail the exam or miss the exam period.