How do I scale a drawing?

Wow, I cannot figure out how to change the scale of a 20 inch by 18 inch assembly drawing such that it takes up about 1/3 of an A sized sheet. I have set up the screen to represent an A sized sheet and bounded the sheet such that it fills the drawing area.

Can anybody help. I completed the training, but it just sets up drawings in metric, then doesn't tell me how to change the scale of the drawing. Thanks. I will try to be smarter in the future.