To schedule an exam, first select the exam that has to be scheduled. This can be done by 

Menu >> Academics >> Gradebook >> Select the Exam Planner &  Show details >> Manage Classes >> Select the Exam & Manage Exams

1.  Select Add Exams.

2. Now enter the exam dates, Choose the sections for which exam has to scheduled and the exam Timings. Activity exams don't have to be scheduled, they just need to be activated.

3. Save Exam Dates.

4. Now create the exam timetable by entering the subjects for which exam has to be scheduled.

5. Select the schedule exams. In case you want to send an SMS Notification you can click on Save and Send Notification.

6. Once exams are scheduled you can start entering marks.