From Vienna :  

A1 towards Salzburg - Walserberg leave the motorway - direction Lofer - Zell am See - Kaprun

Coming from Munich :  

A1 towards Salzburg - leave the motorway at Siegsdorf - Lofer - Saalfelden - Zell am See - Kaprun

Coming from Switzerland :

 Inntalautobahn - direction Wörgl - Kitzbühel - Pass Thurn - Mittersill - Kaprun