AICarriers2 has its own installer which will install it to your FSX main folder. It also comes with manual install instructions, but if you use the installer, you do not need to worry about that. Just execute the installer and install into you FSX folder for now. If you do not have the AICarrier2 Package yet, you can get it from here:
http://www.fsxaddons.com/files/download/8a3a4af7-141d-4320-a2aa-9be7012a972f .
The USS_Nimitz_Ike package is a separate carrier addon that can be used with AICarriers. You should have a folder named USS_Nimitz_Ike or something similar. Inside the folder will be three folders "Effects", "SimObjects" and, "Sound". Copy these three folders and place them in your FSX main folder overwriting when asked.
Also in the folder is a file called "cvn_68_69_.cfg" copy this file and place it in Your "FSX Folder\AICarriers\Conf.d" folder.
After installation, a menu item should appear under "Add-ons" in FSX. From this menu you should now be able to choose the Nimitz.
Don't forget to make sure you also have Java JRE installed (get free at
http://java.sun.com).
Hope this helps.
Trevor