Single wire, self-excite? There usually a bolt hole in the back for grounding the alternator to the engine.
The stud goes to a #10 to #8 ( depends more on strands ) wire that is conneted to the battery. The little plastic plug in with the wire hanging out goes to the ignition key. That way the system isn't trying to charge while the engine is off.
You should have a strap, copper braid or big wire connecting the engine to the battery/frame. There should be a good size wire from the alternator case to the engine block. You should NOT rely on the alternator being grounded...just because it is bolted to the engine.
This is my $0.03 worth ( you get a little extra )
