@PaigePrescott ...

It looks like you are on the administrative side of your Canvas environment.  This area is where all users (admins, teachers, students, etc.) are created as "users".  In this part of Canvas, you aren't defining what role they have in a course.  That is handled at the course level.  For example, if John Doe is listed as a user in Canvas (on the screen that you included in your reply), he can be enrolled in one course as an instructor and in another course as a student.  Many schools have a process in place where users/enrollments come directly from their SIS (Student Information System), so there's hardly any manual account creation, and users can automatically be enrolled in courses with their proper role.  I'm not sure if you have that set up at your school...but that might be something to investigate with your IT department.

Once you have users in your Canvas environment, then if you are manually enrolling them, you do that through the "People" page of a course.

How do I add users to a course?

There is a "Designer" role that comes "out of the box" with Canvas, and you might be able to use that one for your purposes.  Here's an admin Guide that explains more about that role:

What user roles and permissions are available in C... - Instructure Community (canvaslms.com)

I hope this is enough info to help get you started...but please let us know if you have more questions about this...thanks!