Using iStudiez pro on iOS or Android device tap a checkbox left to assignment's/exam's name to mark it as completed and enter your grade. 

On Mac and Windows - check a checkbox left to assignment's name to mark it as completed.
To complete your exam, go to the Planner > Semester > Course > Schedule > open exam entry to edit the details > check a checkbox left to exam's name to mark it as completed and enter your grade.

Do the following to complete your exam on Windows from the Overview: 
Go to the Overview > double-click your exam entry > click "Edit the details" button > check a checkbox left to exam's name to mark it as completed and enter your grade.