However, if you are not able to see the logout button as shown in these guides, then I would recommend that you reach out to Canvas Support.
I hope these resources will be of help to you, Jazzy. Please let us know if you have any questions...thanks!
It's also important with web based applications to close your web browser after logged out. If your school uses a Single Sign On (SSO), it's possible that even after you log out of Canvas someone can get right back in because the the SSO is still active. Closing your web browser will usually also sign out of any SSO systems being used.