eToys questions - creating a sketch for a backdrop image - 'stage'

I have a 'racetrack' sketch that is supposed to work as a 'stage' as
in Scratch. The car drives on this racetrack and needs to leave a pen
trail.
The pendown writes onto the main screen area, underneath this
racetrack 'stage'.  How do I create two sketches - one serving as a
'stage' /background, and the other as the 'sprite' to move and leave
pen trails on the first sketch.
Thanks
Randy Latimer