First, you need to be sure that the output on the wire is DC. It may not be if t was designed to go to an external regulator.
Assuming you have a DC charging current avalable, it can be connected directly to the battery +'ve terminal. Ideally, this should be done with a relay, or a double-pole switch on the ignition so that it's only connected to the battery when the engine is running. This will avoid a 'leaky' regulator/rectifier from draining the battery during extended periods of non-use.
BE CAREFUL not to apply battery voltage to the engine kill wire under any circumstances. If you do, you will need a new ignition coil.
If you have AC on the charge wire, you will need to fit a rectifier/regulator first, then proceed as above.
phil_saunders@bigfoot.com
Phil Saunders
October 2008