While your students are using the site
It's often hard for teachers to stay in the background, being what some call the "guide on the side."
But, this is one time when you might consider this role. This site was designed to offer students a way to master content on their own.
However, their success with the site ... as with anything else in your classroom ... depends on you.
As your students work, you can:
Circulate and observe what is happening.
Interact with individual students, especially if they do not seem to be making progress.
Offer ideas to be considered, not answers to be followed blindly.
Identify peer helpers (technology or content experts) that you can call on to assist other students.