Follow these steps if you want students to mark their own attendance via their Learning Events calendar in Entrada. 

During setup of event, scroll down to Audience Options:

• If the learning event is to be conducted in campus at NUS, select both "Learner attendance is required for this Learning Event" and "Enable Location Attendance Taking for this Learning Event". 
• If the learning event is to be conducted online, select both "Learner attendance is required for this Learning Event" and "Enable Online Attendance Taking for this Learning Event".