Once a student's ID has been verified and they have been enrolled in the course, they can then be activated in the course. Their status will be indicated as enrolled and when you mouse over that button, the choices will be activate or drop. A student is generally made active when they have completed a specific amount of the course (e.g. 5%).
Click the button to open the window. Select the date (default is today's date) and select Activate.
Select the arrow button on the right, or use the Table of Contents, to go to the next screen.