No matter from which direction you will arrive, when you are on A66 take exit Wiesbaden-Biebrich.
From the main station:
At the ESWE bus platform C get on lines 4 or 14 heading for Biebrich and get off at bus stop Robert-Krekel-Anlage.
From the airport:
Use express trains S8 or S9 from the regional train station going to Wiesbaden Hauptbahnhof. From there take the ESWE buses as described before.