I don't understand the question. The train model is already at the correct scale to add person atoms to. They can stand in the aisle, or sit in the seats. The train is a Custom Unity Asset. You can't select a CUA by clicking on it, you have to select it from the select menu. Once it's selected, it can be moved and scaled if needed. I turned off collision on the train model, but I don't know if that's necessary. The 0,0,0 position is in the middle of the aisle. In the screenshot I posted above, the train and person are at default scale.