The Grades tool can be accessed by going to Assessments => Grades, from the main menu.
(Click to enlarge)
The instructor's settings for the course will determine what grades are visible and whether or not you can see a final cumulative grade.
For questions about your grades, please reach out to your instructor directly.
By default, you will also receive notification about updated grades. These notifications will be available in Brightspace under the notification bell, sent via email, and in the Brightspace Pulse app.
(The notification bell in Brightspace).
If you are receiving too many notifications, you can change your notification settings.