Assigning Manager for a lerner

Hi,

As we are new with the moodle. We are facing the following problem.

1. We are am using the "totaralms-2.2.6", we have created a course and added an face to face activity.

2. In the student course page, when we try to sign up for the sesssion. We are facing the following problem. "This session requires manager approval to book."

3. Can you please let me know, how to assign a Manager for the Student role user.

Regards,

Raghu.