Ok, so they ask you information that means nothing for a foreign citizens.
Anyway, the "codice fiscale" it's easy to calculate, use a website like this one, put your name, surname, date of birth and country (Sweden in your case) and you'll have a "tax code": http://www.nomix.it/...ice-fiscale.php
The "n.civ" it's a part of your address.
Example: If I live in "Via Leonardo Da Vinci (Leonardo Da Vinci Street)" the "N. Civ" identify that building where my home is.
Usually in Sweden this number goes first. Ex. If you are a student living in the building number 5 of Fysikgränd, Umeå your N. Civ will be "5".
I hope that this explanation will help you;)