Do you have a product number? I bought a Lionel LionChief O 6-81101 Polar Express (has a remote and a wall mount power supply). In the cab, there is a switch that turns the smoke unit on/off. I have used Lionel Premium smoke fluid and various flavors of MegaSteam fluid. If you have a product number, you can go to Lionel.com, Support, Owners Manuals to get the owners manual. Here is an excerpt from my manual:
'The smoke generator requires the periodic addition of Lionel smoke fluid in order to function. A
small bottle of smoke fluid is included with this set. Press down and unscrew the cap. Pierce the end
of the nozzle with a pin, then add about four drops of fluid directly into the locomotive’s stack. Smoke
production commences momentarily. It will start faster if you run your locomotive at higher speeds.
When smoke production decreases, add more fluid (about four drops). An idle locomotive will not
smoke.'