If your alternator is a Delco you most likely have the 10si. Very common for this alternator to be used in conversions.
If the ampmeter shows a discharge with the key on and the motor not running then moves to the center or off discharge it is most likely working correctly. Very uncommon for the neddle to move into the charge area very much because tractors use very little power and it does not take very long to charge a slightly discharged battery.
If you have a cheap hand held volt meter ($20 at wal mart) you can check battery voltage while the tractor is running to be sure. Should be about 14 volts when engine is running and alternator is charging.
The wires on the alternator.
This is where the power leaves the alternator to charge the battery. We usualy use the starter relay as a place to connect this wire to the battery because the large battery wire is hooked here anyway.
This is the field wire. Power comes into the alternator on this wire to activate or excite the field wires so the alternator will start charging.
This wire needs some kind of way (one way diode; idiot light)to prevent current from flowing in the opposite direction because it is hooked up in the same place as the coil. If you do not include this when you turn the key off the alternator will supply power to the coil and the engine will not shut down.
This is the stator wire. This is where the regulator reads the charge of the battery. In a car this wire is run back into the wiring harness and then spliced into the battery wire. This is done to so we can get a true reading of the battery charge and do not have to adjust for current drop over a long wire. Since a tractor has very little wiring we do not need to worry to much about current drop. So we can just take a small jumper wire and hook the #2/S post directly to the battery post on the back of the alternator.
So the short answer would be the 2/S wire hooks to the battery post on the back of the alternator.