How to do a simulation using Importance or weight window according "examples/extend/biasing/B01"?

Particles, Track, Event, Run and Biasing
1

i want to do a simulation about deep penetration according “examples/extend/biasing/B01”,
the SteppingAction class is used in the application,
the code below:
“for(G4int i=0;i<20;i++)G4cout<<“SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS”<<G4endl;”
is added on the SteppingAction::UserSteppingAction(const G4Step* step) section,
aften running the application, nothing happened about the code up,
it seems the SteppingAction class is not executed.
so how to do a simulation using Importance or weight window according “examples/extend/biasing/B01”?