How to change the role of a user to become a learner in the course?

You may want to assign your course to instructors. Some of the users have the instructor role in the TalentLMS portal. 

To do that, you need to have access as an admin. Then,

1. Go to the respective course.
2. In the Users tab, search for the instructor's name.
3. Click on the role Instructor, choose Learner and click on it.