Once you log in to Canvas, you will be presented with the Dashboard. This page will list all of your "favorited" classes, which by default should be all of them. To go to a specific course's page, click on its corresponding card. When you get invited to a class at the beginning of the school year, the invitation will appear on the dashboard for you to accept. You will also receive an email, which you can also use to join the class. There are additional items on the dashboard that you may also find useful, such as the "View Grades" button.
"I can't find my class!"
If you cannot find a class on the dashboard that you are currently enrolled in, it may be "unfavorited". Click on the Courses button in the menu, then select "All Courses".
Search through the list of courses for the one that you're missing. Courses without an orange star next to them will not appear on your dashboard. You can click the star to "favorite" and "unfavorite" it.