The rail kit has four longer bolts and nuts to replace the existing fender bolts. Begin by removing the existing fender bolts from one side only. Slide the rail up under the fender (the fender sandwiches between the fork boss and fender rail bracket) and install the new longer fender bolts with a little
blue thread locker on the threads, making sure they extend through the holes in the fender rail. Put additional
blue thread locker in the nuts and install on the extended fender bolts from the tire side. (I found it easier in the close quarters to back the fender bolts out a little, place the nut in position, and retighten the fender bolt. This will allow threading through the nut while putting the bolt back in place.) Repeat this process for the remaining two bolts on the other side. Go back and retighten all four fender bolts then tighten the nuts. It is a tight fit with the tire in place but it is possible to tighten the nuts with an end wrench. I also found using a swivel socket/ratchet through the wheel spokes from the opposite side worked too.
While I was at it, I fabbed a stainless steel bracket and relocated my helmet lock to the front fork as well.