That plug from under the tank is the ignitor plug, left side of the top tube. Another note, the tank console harness that you are swapping out does not have any lamps. You must take out the bulbs from your old harness and place them in the one Triumph supplied.
Read the link Phil gave you. The link doesn’t show a picture of how you open the plug up. It used too. Ya have to open it up otherwise you'll damage the wire's end.
