You can take a plane to Frankfurt (FRA) or Nuremberg (NUE). From all airports, you can take a train to Wuerzburg. From Frankfurt Airport, the train takes about 1 1/2 hours and departs every hour. From Nuremberg, the train takes between 1 and 2 hours and departs almost every half an hour.
Normally, you can reach Wuerzburg really easy by train.
A map how to reach Wuerzburg by car can be found here or a more detailed map of franconia here.