you need a rivet gun for the rivets...
something like this. i dont know the exact size you need:
Amazon.com: rivet gun
you can also use traditional nuts/bolts/washer. place your car on ramps, chock a tire. then go under the car, mount the deflector where the large tabs go into the bumper. then mark your holes for the fasteners and drill. there's plenty of room inside the bumper where you will be able to tighten the nut without removing the bumper.