Public transport:
The most sustainable travel option is by train (coming from Villach) to Hermagor. From Hermagor, you can then reach the town of Tröpolach with the station shuttle as well as the bus / ski bus.
Alternatively, there is also the possibility to travel by bus from Kötschach-Mauthen or Villach to Hermagor or Tröpolach.
From Tröpolach, take the Millennium Express up, before reaching the ski tour starting point at the Nassfeld Pass state border via the ski slope descent.
Details at - Nassfeld Mobility Info and Kärntner Linien Route Planner
Travel by car:
Coming from Hermagor or Kötschach-Mauthen, drive via the B111 (Gailtal Road) towards Tröpolach/Nassfeld junction - from there, continue via the B90 (Nassfeld Pass Road) to the former border crossing.