Okay, so it's simple: first we build a base on Titan as the transportation hub for the Saturn system, and transfer there to get to Enceladus [autocorrect wants to change this to Enchiladas].
Wouldn't it make sense to have a methane mining base on Titan anyway?
Refueling on Titan might make a lot of sense. Getting methane is pretty much just a matter of piping it or freezing it out of the atmosphere. Getting oxygen from the CO2 in the atmosphere would be an industrial process and require considerable energy but it beats having to carry the oxygen with you.
Wouldn't it make sense to have a methane mining base on Titan anyway?