If you do not already have a Canvas account, you need to create an account before you can log in to Canvas.
If you are using Canvas through your institution, you most likely already have an account and need to accept a course invitation. Your institution will email your login information. If you do not yet have an account, you can create an account when you accept the course invitation.
Then, in Canvas:
Students click the CodeMonkey link in their classroom.
Select "Open in a New Tab."
Authorize CodeMonkey (they can check "Remember" to skip this step next time).
Click on their class and start the assigned lessons.