You find all important information here.
Linies to the airport: S8 and S9 in the direction of Wiesbaden, approx. 10 min traveltime. The S-Trains are located in the central station. You will take the escalator downwards next to McDonalds to reach platforms 103 and 104. Arrival will be at Terminal 1. To get to Terminal 2 you can take the free shuttle buses and the railway in the airport.
Lines to the fair: Tram 16 direction Ginnheim, Tram 17 direction Rebstockbad, U4 direction Bockenheimer Warte. Destination: Festhalle/Messe.