Just looked at mine (I have the same light plus the Senso option and the same hub) --

The headlight's ground wire -- with the white stripe -- is in the ground receptacle on the hub's plug. That's the hole towards the front since the plug is on the starboard side of the bike.

I still have the screw installed; I thought I might need to remove it, but it works anyway. I have both taillight wires attached to the tabs on the left side -- striped (ground) on back/bottom, and plain on front/top.

When the switch is off, the system is off. The Senso circuit works, but I end up leaving it all On anyway since I think the headlight helps me stand out from the visual clutter and shade in my neighborhood.