Final answer:
The incorrect step in preparing a Lemonade dispenser for use is wetting the evaporator base with a clean, sanitized towel, as this is not a typical or advised step in setting up the dispenser.
Step-by-step explanation:
The question involves identifying the incorrect step in preparing a Lemonade dispenser for use. While steps such as reassembling the pump and attaching it to the bottom of the dispenser, wetting the bowl gasket, and placing it properly, as well as attaching the spray tube assembly, are all legitimate steps in the set-up process of a beverage dispenser, wetting the evaporator base with a clean, sanitized towel is not typically part of this process. In most dispenser setup instructions, the evaporator base is not something that would be wetted as it is usually a part of the machine where the refrigeration happens, and moisture here could be counterproductive or even damaging.