You can use the attendance tool in D2L Brightspace to track attendance.  Click "Course Admin", "Attendance", and then set up your roster.

Please visit D2L's Help topic to learn more about the attendance tool.

If you'd like to use an alternative procedure, you could also track attendance by creating grade items that correspond with the dates of your course, and then you could use numerical values and provide points for attendance.  You could also create a grade item and choose "text" as the type of grade item, and type "P" for present, "A" for absent, "L" for late, etc.  Some instructors prefer to create a spreadsheet and list the student's names, and take attendance that way.