WW2 sites are 2.5 KM away from Bastogne, pretty outside, so the best thing is to take a taxi.
Ask to call it at the Information center in the main square, you will recognize it, there's a big blue and white "I" outside.
The price is about 7 EUR one way.
Bastogne is located in the extreme East of Belgium, almost on the border with the neighbouring country Luxemburg. You drive past Bastogne if you travel by car from Brussels to the city of Luxemburg or vica versa.