If students add your course, realize there may be a 1-3 day delay before their registration is passed to Canvas. If they need access to your Canvas course sooner, you can add them manually using their email address
People > +People
NOTE: if students have been added to your course through the automatic feed from APR to Canvas, you, as a Teacher, cannot remove remove students who have dropped the course from your Canvas course. Once that Drop is processed by the Registrar, the automatic feed to Canvas will remove them from your Canvas course
Course Management at End of Semester
Note that students will by default maintain read access to your Canvas course after the term ends (a couple of weeks after the end of Finals)
If you care to change this, you can in Settings, under Participation, by checking "Restrict students from viewing course after term end date"
If a student will need additional time to submit materials to a Canvas course to satisfy an Incomplete, this article covers how to set that up: