When a student logs into your lesson, you will need to admit them into the virtual classrom.  On the whiteboard vertical toolbar you will see different options.  The bottom option is "user list". When you click on this, you will see who is available  to join the classroom and you can admit students from here. When a student is admitted, you can control to show or hide their video easily. You can also control whether to allow the students to speak or not depending on the type of lesson and number of participants you have.  Even if students are muted, they can still write messages, ask questions and comment using the messaging feature on the right-hand side of the white board.