The figure is a trapeziod. Start off by drawing a vertcal line on the left hand side of your page - about an inch long. At the top ad bottom of the line draw horizontal lines - so you make your two right angles. Now you need to make sure that each side is a different length. Draw the bottom line to say 3 inches and the top line 2 inches. Then connect these lines up.
Wikipedia has a nice diagram - just search trapezoid. In the diagram shown, imagine "h" is the left hand edge of your shape - ignore the line AD.