Your assessment scores will generally be available in two locations, depending on what your instructor has permissioned to be released and when.
Off the Menu on the left-hand side, look to the bottom and you'll see an option for 'Insights' near the bottom. Click here to be taken to the Student Insight Center which includes, amongst other data, your recent assessment scores by lesson as well as your average score to date from all assessments that have released scores.
On the lesson pages that include the assessments themselves instructors may make available your assessment responses, the correct answers and your score on that assessment. Note that this is up to the discretion of your instructor and, even if scores are released, you may have to wait until all students in your section have completed the assessment before you'll be allowed to see your scores and/or responses.