The Hartsfield-Jackson International Airport International Terminal is located at 2600 Maynard H. Jackson Jr. Blvd. and handles all international flights into Atlanta separate from the domestic terminal building.
To get there on MARTA, take any southbound train to the Airport MARTA Station, which travels directly into the domestic terminal. Exit the train and go down the escalator/steps to exit the station. Turn right after going through the fare gate to enter the baggage claim area in the South Terminal. Immediately turn right again and exit out of the building (W-2 door), making sure to follow signs to Ground Transportation. A shuttle bus is available just outside the door that is clearly marked as the international shuttle.
If you are arriving at the international airport, again, follow signs to ground transportation/domestic airport shuttle. MARTA is just inside the airport once you arrive at the domestic terminal. Or take the SkyTrain in ground transportation to the rental car center and two hotels.