You bought the wrong material. The original Capcom Airborne entrance ramp material was stainless steel. Most other manufacturers used blued steel. The blue is on the steel to prevent it from rusting.
BUT you can still use the blued steel (do NOT remove the blueing) and it will work just as well, it just will look sightly different that the other ramps on your Airborne pinball game.
Rivet it on with a rivet press. Do NOT use a pop rivet gun as the ramp won't lower correctly and the pop rivet will dig into the wooden playfield under the ramp.
Good luck,
Steve