First, they should click on the Add a Coach link at the bottom of the page.
Then, they should enter your Coach ID in the form that looks like this:
Your Coach ID is {{ coach_email|escape }}.
Finally, they need to click the Register Coach button. It looks like this:
Once students make you their coach, you'll have access to all types of interesting data about their progress and achievements.
You can access that data via the Class Report.