It is only possible to delete exams from Practique that do not have results assigned to them. If you need to delete an exam that has been sat, first you will need to reset it. See Resetting Exams.
The exam must be in 'In Preparation' state
Click 'Advanced'
Click 'Delete Exam'
Confirm deletion.
Once the exam is deleted, it is not possible to restore it to the system easily.