From airport's exit go straight. At the end of the road turn right to enter the Heraklion- Agios Nikolaos National Road. After 30Km you are at Malia.
From Malia to Heraklion Airport
From Malia, to reach Heraklion Airport you need to follow the Agios Nikolaos - Heraklion National Road. Shortly before you get to the city of Heraklion, you will see the exit to Heraklion Airport on your right. Take the exit, and Heraklion Airport is half a kilometre further on.