You have selected a MacIntosh computer with an Intel processor as your X-Plane platform. Now please choose the type of GPS device that you will use.
Garmin GNS530 Trainer.
Software GPS simulator running on a Windows computer (or a Windows emulator).
Real GPS device, such as this
Garmin GPSMAP 296. Must understand aviation protocol over a serial connection.
Moving map software, such as
PocketFMS running on a PDA, or other devices that understand NMEA sentences over a serial connection.