To view the "Grades" page, just click Go To -> Grades.
Here, you'll see a list of your students. Clicking a specific student's name will bring up that student's grades page. You'll see all teachers connected to that student, along with all classes that student is currently in and the grade the student has in each class.
Clicking on a teacher's name in the list will allow an admin to view all classes that the selected student is attached to, with all assignments/assessments/standards that have been created.
Clicking on a specific class under a teacher's name will display all assignments/assessments/standards under that specific class for the selected student.
To print/download performance reports, click on the "Performance Reports" button at the top of the "Grades" page.