you gotta bleach your hair blonde, weigh 18 stone, have a giant furry coat, get the biggest mofo'in earings you can get, get a deep deep voice, apply too much make up and then some guy with a half bald head and glasses will come from nowhere with a certificate.
seriously - go to a dealership reception, they should provide you with the information you seek and more than likely an application form, previous experience in face to face sales would prob help.