Roles are various sets of permissions granted to a user in Moodle. The role you are assigned dictates what privileges you have and what you can control in Moodle. You must be a member of the teacher role in order to assign roles. You can add members to the following roles: Manual Teacher, Manual Non-Editing Teacher, and Manual Student. This can ONLY be done in semester-based course shells. Explanation of the manual roles can be found in the article titled Understanding Moodle Roles.
Select the Assign roles link in the Administration Block of your course.
On the "Assign roles in Course:" screen, you will see a list of the available roles. Select the role you that you wish to manage.
The next step is to type the username or name of the person to be added to the role in the search text box at the bottom right of the screen. Click on the Search button.

The person/people who match the search criteria entered will appear on the right side of the screen under the Search results.
Highlight the name of the person to be added, then click on the Add button in the middle of the screen.

Once added, the person's name will appear on the left of the screen under the existing user's window. To add more individuals to the currently selected role, simply enter additional search criteria in the search text box.
You will see a button titled, "Assign roles in Course." Click on this button to return to the main Assign roles in Course screen.

On this screen you will now see the name of the person you added to the selected role.

- To return to the course home page, select the button titled, Click here to enter your course.