Cut out sheets of paper that are the same size as the sides of the newspaper rack, not including the glass front. Draw or paint your design on these sheets. Metal is not an easy surface to paint on, so the more planning you do ahead of time, the easier this project will be.
Clean the newspaper rack thoroughly. Any dirt or grease left behind will disrupt the paint coat. You may need to remove a protective coating on the metal, as well. Acetone will often remove protective coatings, and sanding will both remove old paint and coatings as well as give the new paint a rough surface to grip.
Cover the glass window or any other parts that you do not want to be painted with masking tape and newspaper.
Coat the entire rack with a metal primer. Wait for it to dry completely before continuing.
Spray the rack with your base color. If you make stencils or cover parts of the rack with paper or tape, you can use more than one color.
Add details and designs using a brush-on metal paint. Refer to your diagram as you paint. Wait for all of the paint to dry completely before continuing.
Coat the rack with a layer of clear spray lacquer. This will protect the paint.