From another thread on this, here are the "Fez's Realistic Roll-Bar Install Guide"
It isn't difficult but it is time consuming to jack up the car, remove wheels, remove the seats, remove rear panel stuff, trunk stuff, fit bar, mark holes, drill holes, re-fit, wonder why it is off a little bit, search on the internet for answers, have a beer, order pizza, look for the drill bit you dropped in the nether areas of the trunk, chase the kids out of the garage, run to the parts store for the drill bit you gave up on finding, drill the rest of the 16 holes needed, fit bar for the last time, bolt down 4 bolts, remove bar when you realize you need to remove the seat belts, look for the tiny clip that fell off the seatbelt assembly, decide you have had enough for the day and vow to start again in the morning.
Wake up stiff from all the contortions of the day before, look at your Miata and wonder if it is worth it, go inside and refill coffee. Come out an hour later after calling your buddy to get his ass down to help finish this up, cut on the metal panel where the rear supports go after trying to make sense of the drawing that came with the roll bar, look on the internet for what everyone else did, cut off more than necessary but decide it will all be under the carpet and no one will see it anyway, ream out some of the holes that aren't quite big enough for the bolts to go through, cuss at Hard Dog for sending the wrong backing plates, look on the internet to see what everyone else did to resolve this. Realize backing plates are just swapped left-right and they fit just fine. Drop backing plates on face when fitting them under the car. Chase the kids out of the garage and explain to them why they do not need to help. Get the bar lined up, fitted and mostly bolted down. Spend the next hour torquing all the bolts. Stand up proudly and realize you need to re-install the trunk carpet and fiddly bits, look at the plastic trim panels and decide to cut them nicely next weekend, install the rear panel, cut rear carpet, realize you cut too much, look on the internet for a spare bit of carpet and order it from E-Bay. Install seats and go for a drive. Bang head on roll bar and learn to get in without doing that again. Decide you want to trim the plastic panels today so you study the template for an hour before taking the plunge. Go back on E-Bay and order spare trim panels after cutting too much off of them.
For the next 12 months, listen to the rattle of the drill bit you couldn't find as it bounces around near the gas tank.