So, quick install instructions:
Remove your seat and the two nuts from the fender bolts that stick up under the seat. Retain the nuts.
Carefully lift your ECM out of the battery cover and move it out of the way. Just unclip it to make room to work. You don't need to disconnect anything.
Take the mounting bracket out of the small plastic bag and install it with the attached bolts and nuts to the two holes on the frame just behind the battery cover. Be careful not to drop the nuts as they will try to bounce down into some very difficult to reach places, leading to much profanity. Replace ECM into it's original location.
Take the backrest bracket and place it so that the front hole lines up with the top hole in the bracket you just installed and the two fender bolts come through the holes on the rear of the bracket. Secure it with the bolt and nut to the mounting bracket and the two nuts you removed earlier. You will use 2 washers between the bracket and the fender nuts. If you haven't already, detach the cable for the adjusting lever from the bracket.
Take the spring clip, washer, and nut off of the mounting plate for the adjustment lever. On the frame, under the seat, you will see a large hole with a smaller hole just beneath and to one side of it. Looking from the front of the bike, it will be in the upper right corner. CAREFULLY install the spring clip through the larger hole so that the threaded hole in the clip lines up with the smaller hole in the frame. There will be profanity during this part. Possibly some scratched paint, and nearly certainly a small amount of blood from at least one skinned knuckle. Hopefully you have a small magnetic probe handy as it will make recovering the spring clip you dropped from the primary easier... Seriously, this one small part of the install took me longer than the rest of it put together. You will also have to unclip one of the spark plug wires from the frame to make room for the bracket. Once finished secure the spark plug wire. I used a cable tie to secure it to the clip on the other wire.
Route the cable for the adjustment lever through the frame, into the battery compartment, and along the fender until you can attach it to the lever on the backrest bracket. I secured it with cable ties to the frame and the bracket to keep it from vibrating as much as possible. Mount the adjustment lever bracket to the speed nut you installed in the frame with the bolt and washer. It makes it easier if you remove the lever from the bracket and have one of those ratcheting box wrenches.
Take the square plastic "seat protector" (that will be in a separate envelope, Oops) and using double sided tape figure out where to place it on the underside of your seat to protect it from wear from the backrest as it is folded forward and back. You will see where the pivoting section of the bracket can come in contact with the underside of the rear seat. Mark the location and then using an adhesive of your choice attach protector to the seat. I had it on my stock seat but never bothered to obtain one for my Sundowner, which is the seat I actually used the backrest with the short period I used it.
Install seat and insert backrest into the slot in the bracket until it locks in place. There is an adjustment on the back of the backrest for height, but unless you play for the NBA I'm not sure you'll ever need to adjust it up.
Be advised, the backrest adjusts forward rather...aggressively...when you pull the lever. Apply resistance against the backrest to prevent it from coming forward harder than you'd expect. The rest will fold forward without needing to pull the lever and then spring back to it's original position to make it easier to mount the bike without removing the backrest.
Best regards and I hope you enjoy the backrest. Sorry about the seat protector, I'd set it on my desk while I was finding a box to put the backrest in so I wouldn't forget it... I'll drop it in the mail first thing Tuesday when the Post Office reopens.
