If the alternator you bought doesn't have two identical spade connectors, the terminal without the spade is probably already grounded. Check the resistance between the spade terminal and alternator case. If the resistance is 10 to 20 ohms, it's already grounded. If there is no resistance, just take the screw out of the terminal with no spade lug, remove the insulating washers and put the screw back in, then connect your regulator to the spade terminal.