Exams must be published only after you’ve made sure that all necessary settings have been made and all questions have been added. Changes can be made to an exam even after publishing it and as long as no student has taken the exam. You can publish an exam immediately after creating it or at a later time.
Click the module access icon > Academics > Examination > Online Exam > View Online Exams to open the View Online Exams page.
Select a batch.
Click Publish beside the exam you want to publish.
Click on an exam name > More button > Publish Exam.
For more information, view this: