And the TUBE, wire only ONE of the TWO pins on one end..
I think if you wire two of them also ok. They are the same. there are two points so that we can twist and lock it on the bracket. The three point switch, is it the three position ones (pic). If it is, just wire to the centre leg and any one of the side ones. The best way is to test with a bulb. Or a ohm meter if you have one.