Hi there, @BirgitNewman ...
This is probably a better question to ask your school's IT person (or whoever helps with getting accounts enrolled in your school's Canvas environment). For us, all our user accounts are added first through our SIS (Student Information System), and then those accounts are passed along to Canvas. If you had a rare instance where someone outside of the school needed access to a course in your Canvas environment, your Canvas administrator could manually create an account for that person and then enroll him/her in one or more courses. Depending on how your school's login process is set up, your school's Canvas admin may need to provide a different URL for this person to get logged in. It really depends on how your school's login is set up, so this is why having a conversation with your IT department or at least someone from your school's Online Learning / eLearning / Distance Learning team will be helpful.
Hopefully you'll be able to connect with someone at your school soon. Good luck!
