You can visit the Lassithi Plateau in various ways.
By ship
There is a ferry connection through regular roures from the port of Peraeus to Heraklion
For more information here
By Bus
There is the possibility of transportation via KTEL(Bus) with final destination Lasithi Plateau.
For more information here
By plain
Those who wish to travel by air, have the option to fly to Heraklion and then by bus with the final destination of the Lasith Plateau.
For more information here
By taxi
Also, you can use local drivers (taxi) to take you to your desired destination.
You can book your own driver here