Adding items.

Hi.
Sorry for posting about a common subject but can someone please link me to a tutorial to adding items to a mod? I have literally no experience whatsoever modding anything as complex as M&B. I have been searching for a tutorial that leaves nothing to my own knowledge about the subject but my attempts have yet to bare any fruit. All I want to do is add the plate armor and warhorse from the native game to Brytenwalda. I assume it won't take more than 5 minutes but I can never understand how to do it, mostly because all the tutorials I've seen are ambiguous, dealing with .py files that I have no idea how to acquire or where to find, as the directories seem to differ in every tutorial.
Thank you.

Download Morgh's editor from Tools sub-forum, open Native module, write down item stats, open Brytenwalda module, add new item, edit it's stats to match Native version, save.

Not the fastest method (it would be much faster to just copy item entries from Native's item_kinds1.txt to the end of Brytenwalda's and fix the total items counter at the start of the file) but one with the least chance to break something.