You'll likely want to review the video at the top of the third page of Lesson 0, as it explains how to use the course. Each exercise (like the super imposed lines, ghosted lines, etc) have specific numbers of pages assigned (in the homework section that links off to their instructions as shown here, so that's the quantity you would complete before continuing on. This is explained in the video (which is quite important), so if you missed that information there, the video as a whole is likely going to be something worth taking a second look at.