Sketch the scene you desire on paper, determining composition, color and detail. If this is your first painting endeavor keep your sketch simple.
Measure the area on the shed on which you want your scene to appear. Divide the area into four quadrants, drawn on the shed lightly with pencil or a grease pencil.
Divide your sketch into quadrants.
Rough out the quadrant on the shed that corresponds with the quadrant on your sketch. Repeat this process with the remaining three quadrants.
Fill in the sketch on the shed with the desired colors, using enamel paint and beginning at the top of the scene and working down.
Use turpentine or paint thinner to clean your brushes.