Installing fans on the bottom bracket is indeed a bit of a chore, you need to put the case down on one side to get at a few screws that hold the bracket in place. As for the led cables, theese are indeed for connecting up the led fans at the front of the case, should you add any more of the phanteks led fans the extra leads are for those. No need to connect any to the hub. There is another molex cable labeled 12v, this is for the front and top panel led strip. The cable marked led strip is for an optional light that can be purchased separately.