You can place objects if you type "build1", it places the object, if you want to remove it just type "build1" again and the object will disappear. I also include interior parts too but it better to place it to the sky.
Note: If you save the game after you place the objects in wrong place like blocking the road or interior or something like that, it will be stuck forever in your current save file.
Just type them what you see below: