What are the approximate dimensions of the apron aircraft zones, ramp, aircraft stands such as Airbus A380, Boeing B737, F16.
Further, there is special CAD software for the design of airports. This includes the turn radius planning for a large number of aircraft.
Finally, because of the complexity and the large number of regulations there are companies, that specialize in airport planning and design.
Or you could always just wing it like the Germans and be ten years late and six times over budget and still incomplete ...