The resistor wire is between a short wire from the ignition and the positive terminal on the coil. The short wire is full 12V - the resistor wire drops it down to about 9.5V (sometimes the car needs to be running for you to see this drop as the wire needs to warm up slightly).
The tach lead goes to the negative terminal on the coil.
If using a pertronix, or if your distributor has a negative wire, it also goes to the negative terminal on the coil.
The positive wire from the pertronix (red) or distributor can go to the positive terminal on the coil, however sometimes it is better, or required by the manufacturer, to splice it into the short wire between the ignition and resistor wire for a full 12V.
If you know the current going through that wire you can calculate the resistance of the wire based on the information above using ohms law. One way to check it would be to hook up a multimeter and measure the current and the voltage too, some multimeters can measure resistance, so you wouldn't even have to bother with the formula. If you don't have one, they can be found cheap. I got mine for like $20 at Home Depot.
I believe it is .8 ohms. I would have mentioned that, but I just think he is barking up the wrong tree to get his car started and didn't want to distract him from the basics - Is it wired right?