Instructors will often leave feedback on assignments that students can review from the course "My Grades" page. To do this navigate to the course and then go to Tools > My Grades (Your Instructor may have a shortcut created to your My Grades page, you can use it as well).
Quizzes & Tests
Assessments such as Quizzes and Tests will display a blue "Speech Bubble" icon that you can click to view feedback. You can also click the title of the assignment to view any feedback left for individual questions.
Submitted Papers
Submitted Papers can have multiple notes from instructors. To review these, click on the title of the submitted paper. This should open the paper and instructor feedback will be marked with another speech bubble icon. Click this icon to view the instructor comment.