To get the ship into AICarriers all you need from the Kongo download zip file is the "ai_IJN Battleship Kongo" folder. Copy that to your FSX SimObjects/Boats folder and ignore the rest of the stuff for the time being. Frank covered the other things to check. Here is the Kongo entry in my aicarriers.cfg file and it shows up fine in my sim:
[formation.45]
title=IJN Battleship Kongo
unit.0=ai_IJN Battleship Kongo, 0, 0
The "title=" line is free text, you can call the formation anything you want. I could have called it "Kongo Steaming Independently". However, on the "unit.0=" line you have to use the ship's title from its sim.cfg file.