Mind you, some of these pictures are dated, but still applicable.
I am on my 2nd chin spoiler, as my 1st one got grenaded by the mother load of all raccoon's a couple of years back, which took out the right side, the right LED marker, and the right front wheel well liner.
In a very quick explanation, essentially, the chin spoiler acts as a replacement for, the factory front lower piece, which is textured/dimpled craptastic plastic.
You can see it in this image below, in which it's still attached to the car, and the aftermarket custom chin spoiler piece is place onto the ground below it.
To remove this piece, you'll have to jack up the front end, crawl underneath, and scope out all the flat tabs that are located all around the factory piece, where it fastens it to the bottom of the front bumper clip.
You'll have to disengage these tabs (I think I pressed downwards on them) to dislodge them and free the lower cladding piece, from the front bumper clip.
Also, IIRC, there are small screws all along the bottom of the factory cladding, which helps fasten the smaller of the two under belly pans, to the cladding. You'll have to remove all of those as well.
Once you remove the factory piece, it will look essentially like the following images (note all the slots where the tabs from the cladding pressed into the lower front bumper):
In these pics below, you can see all along the bottom of the front bumper clip, a channel which looks like a backwards letter 'c'.
You will want to position the top part of the custom chin spoiler (which has a 90 degree, horizontal edge all along it's top, and mate it into this channel.
From the backside, or from underneath the car, my body shop guys and I, filled this entire channel with a VERY STRONG 2 part epoxy/adhesive, which literally had a working window of approximately 15min before it started setting up and/or hardening.
I don't know what that stuff was called, but the adhesive/caulking gun the shop used held two cans, 1 part of each, and it mixed together as it was coming out of the gun's nozzle.
Looking at the last of the 3 pics immediately above, you note on the far back side a piece of metal.
This was just flat metal stock, that we custom cut, then bent into an almost 90 degree, and used the same two part epoxy to fasten it to the backside of the chin spoiler, then we used a pop rivet to fasten the front part of the wheel well liner, to the spoiler.
Now we did use painter's tape as a means to fasten the chin spoiler, to the front bumper clip, albeit it temporarily, as we were running out of hands so to speak.
That's about all I am able to contribute to your request for install help.
There weren't any directions in either of my order's I placed for this item.
Not for the 1st time I ordered it, nor for the 2nd time when I had to replace it after the raccoon took it out.
You'll have to figure some of this stuff out on your own, as it literally is a custom job to get this piece installed properly.
If you have additional questions, as they should arise, I might be able to lend assistance accordingly, but the above is it in a nutshell.
It should look sharp once it's completed though.
