Good evening, @LisaNoble ...
When someone is enrolled in classes at two different schools that both use Canvas as their LMS (Learning Management System), there is no way to toggle between the two using the same login information. Generally, one school will provide you instructions with your username/password to log in to their Canvas environment, and the second school may have a similar or somewhat different way to log in to their own Canvas environment. The URLs for each Canvas environment will also be different. For example:
https://SchoolNameOne.instructure.com vs. https://SchoolNameTwo.instructure.com
You will want to review each school's documentation (which may be found on each of their websites) to determine how you need to log in to those environments. Hopefully you'll be able to locate this information soon. Good luck to you!