From Munich Airport by car:
Wildbad Kreuth is about 100 km by car south of the Munich airport. Take A9, A99 and A8 to B318 in Holzkirchen. Take exit 97-Holzkirchen from A8.Follow B318 and B307 to Wildbad Kreuth
Look it up in google maps.
From Munich Airport by train:
The airport is connected via S-Bahn (local train) to the Munich Central Station. Take either S1 or S8 until München Hauptbahnhof and follow the directions below for reaching Wildbad Kreuth from the Central Station by train.
The S-Bahn leaves every 10 minutes and takes about 40 minutes to the Central Station.
From Munich Central Station by train:
Take the BOB from Munich Central Station to Tegernsee. The train runs daily from about 07:05 in the morning to 16:05 in the evening once per hour and takes about an hour to Tegernsee. Please note that the train splits in two parts in Holzkirchen and only one part proceeds to Tegernsee. From Tegernsee take the bus 9556 (20 min) or taxi to Wildbad Kreuth.
Look it up on the travel page from the German railway (DB).
The tickets for the whole journey you can buy from vending machines or at counters in the airport. It is possible to buy the tickets for Munich S-Bahn, BOB and bus 9556 separately, but a better alternative is Bayern-Ticket (23EUR, +5EUR for every extra person, max. 5 persons, valid from 9:00 till 3:00 of the following day on weekdays, from 0:00 till 3:00 of the following day on weekends and holidays), that will cover the whole journey from the airport to Wildbad Kreuth.