Question about measuring current

[christian]

So all this talk about ammeters lately has me now questioning the unit in my model A. I have a brand new voltage regulator cutout from fun projects I'm about to install and would like to calibrate the third brush using my digital multimeter instead of the ammeter in the car. So my question is, i set the multimeter to current, then measure from where? Does it matter ? I only use one lead from the multimeter right ??

If you can't tell, I'm not really good with electronics