Is there a guided tour?

Yes. Click "Guide" at the bottom of the sidebar and choose the tour "Activity Studio: puzzle books" (it is marked "this page" while you are in Activity Studio). Start it while your color by number book is open: it points at each part of the screen: Print check, The book, The designs, Color by number, Pages, Cover and listing text, AI drawings, A page from a photo, Color it in and Every design, and ends with "A book worth buying".