Fuel cleaner/additive for Onan generator

Servicing my Microquiet 4000 Onan gas generator and wondering how to use fuel cleanser for generator? Pour in RV tank, or disconnect fuel intake line at generator and introduce additive that way (provided there's a fuel pump in generator....not sure?). Didn't want carb to gum up over time and use. And, what type of fuel additive have you folks used for this purpose? Thanks in advance!