I have been chasing invisible electrons for 40 years [electronic technician]
You absolutely need a multimeter or at least a 12 volt test light
On the fuses that I have seen, there is a bare spot on each end
On end of voltmeter/test light on ground. Now place probe on each bare spots , one at a time, on the fuse. What do you see?
Still confused? Go to Youtube and there are multitude of videos of varying quality out there.
Type in search alternator, battery, multimeter this ought to get you going
BTW get the cheapest multimeter