I have never done this but I would mount the switch on the left side of the fairing so you can leave your hand on the gas/brake. Wiring could not be easier. Get a SPST switch (which only has two leads). Find the radiator switch, it's the only electrical device attached directly to the radiator (not the fan). The radiator switch will only have two wires. Wire the SPST switch leads to the radiator switch in parallel, one wire per lead, leaving the radiator switch still attached to the wires. E18 connectors make this process quite simple. It does not matter whcih switch wire goes where as long as they are not shorted together. One caveat, the power to the radiaotor switch may be constant so it could be possible for someone to turn the fan on while the bike is parked and drain your battery.