By metro line "C" to the station "Nadrazi Holesovice".
From here one stop by tram 5, 12, 14, 15 or 17 to the tram station "Vystaviste".
Or from "Nadrazi Holesovice" 15 min walk (ask for direction to "Vystaviste").

Prague Public Transit Co. - excellent webpages about Prague public transport (in English)