Walk. There are no buses and to the best of my knowledge no taxis wait at that station. I may be wrong.
The distance is about 4km.
I would have said that it is upwards of 5 km, nevertheless cubsur is correct in saying that you have to walk it. Turn right outside the station and turn left at the crossroads (where Rocamadour is signed). There is another road junction a little before you get to Rocamadour itself but by then you can see it in the valley below - you can either drop down into the valley on the road or stay at the upper level and go down into the village using the elevator (or the steps).
Thank you to all for your information :)