Mela, thanks for posting how you resolved the problem, as the info can help others with the same problem.
Regarding understanding roles and permissions, you're welcome to experiment with them on our Moodle sandbox demo site where you can log in as an admin in one browser and as a student or teacher in another browser then check any changes. The site resets on the hour, so it's good to start experimenting just after the hour to give yourself plenty of time!