I just purchased a 2-10-0 Decopod that came with what I think is a smoke packet, but there is no instructions as to how to use it, or even if it is applicable to the 84302 model.
If the packet contains liquid It is smoke fluid. You put a few drops in the smoke stack. However I do not use smoke as it leaves an oily residue on the track which can be tough to clean.
IF that packet contains a powder, that is meant for weathering your loco, too make the coal load look better.
Smoke fluid would come in a small plastic vial.
I do not believe the Bachmann 2-10-0 comes with a smoke unit.
However,,with a paintbrush or q-tip you can use that powder to simulate soot in the smokestack.
The 2-10-0 does not have a smoke unit nor does it come with smoke fluid. The small bag with powder has material for weathering the loco if so desired.