I was confused too, but I'm stubborn, eventually figured out:
Clicking "Draw Fast" creates a box with the label "a city skyline"—drawing in that box will render an image to the right as you draw.
Double-clicking the box that "Draw Fast" produces allows you to edit the tag which says "city skyline" by default—allowing you to change what it renders as you sketch.
Clicking "Draw Fast" creates a box with the label "a city skyline"—drawing in that box will render an image to the right as you draw.
Double-clicking the box that "Draw Fast" produces allows you to edit the tag which says "city skyline" by default—allowing you to change what it renders as you sketch.