You can see how you did on an individual assignment by going to your My Assignments page and scrolling to the bottom section, Completed Assignments. Click the assignment to see how you did on each question, and swipe past the final question to see your total score.
You can see how you've done on all your assignments at a glance from your My Performance page.
On this page, assignments are categorized as submitted or incomplete. Check the due dates of incomplete assignments to make sure you are keeping up with your work.
On the Submitted Assignments table you can see your overall score and your average on multiple-choice and short-answer questions. You can also click View Response(s) to see how you answered short answer questions and what feedback your teacher gave you on your writing.
Finally, at the bottom of the page, you can track your performance on particular skills. Use the dropdown to choose a skill and learn about what assignments have gone over that skill and how you are doing on it.