The reason there are no students in your attendance currently is because you have not enrolled them in the section that you are attempting to take attendance for. As you can see below, there are no students enrolled in Section 1.
All of Chalk's applications (Planboard, Markboard and Attendance) are connected for the semesters that you create. To add students to your class, you will need to enroll them in the section that you are trying to take attendance for through the Markboard application.
Click the Add Students button in the centre of the page.
Continue onto How do I create & enroll students into my class?