http://www.cars.gov/index.php/dealersupport
Ah yeah, sorry about that. Evidently the dealers are sent a letter with the link to the dealersupport area. I of course cheated and got the link through a search.
Evidently the auto makers submit a list of dealers to the government, who in turn sends them the website address. They then have to register for the program, get their login info, etc.