Ok, first off, as with any car of it's time period, the electrical system is pretty simple. Your best bet is to try and look up the wiring diagram for that year and model (a 2 door '67 LTD is pictured above). But before you can use it, you need to understand how DC electrical circuits work, how power is routed through the car.
There are a few wires to the engine. Actually, what you have is a wire from the alternator to the battery, wires for a couple guage sending units, a ground link from engine to chassis, a wire from the starter up to the starter solenoid in the engine compartment, and a wire from the solenoid to the battery, as well as a small wire from the solenoid to the key.
As for rust, if it's small amounts, just identify it, clean up the loose flakes, and spray it with a rust converter product (that turns it to a black zinc oxide primer) and let it be for a while. If it's bad, you'll need to cut it out and replace panels, but really, unless you can see through it like a window, deal with the mechanical issues first.
Those cars are extremely simple, but some parts can be expensive to find. Don't worry, as you don't need every part of the car to be new to enjoy it.
Go here: http://auto.howstuffworks.com/under-...od-channel.htm
and learn how the systems work.