How can I see Grade Center activity in Base Navigation?

To see your Grade Center activity from Base Navigation, select "Grades" from the Base Navigation menu.  From there, you will see recent activity, such as submissions that need grading.  You can select the course name or submissions to go to the Grade Center.

Alternatively, you can grade how you always have by entering your course from the "Courses" menu and select one of the options under "Grade Center" from your course menu.