Drill two small holes in the jar lid or cork. One hole will be for the wick and the other will allow for release of pressure from the container as fuel leaves it during combustion (although if your cork is loose enough, this isn't strictly necessary and one can find many differing designs for alcohol lamps on the Interwebs). Retain the other lid/cork without holes to seal the container when not in use (to prevent evaporation of the ethanol).