Look up Morgh's Editor for warband. Do not use the module system since they have not released that system for this mod. I love to see you taking the time to do this yourself so am going to go step by step for this mod.
unzip the tool and click on Morghs M&B WB-WFAS Editor.exe in the folder. On the first screen of the tool it will have a Configuration button at the bottom above exit. Click that and point it to a COPY of Warsword Conquest in your module directory. Save Configuration and it will open the rest of the tool. Click on Item editor. The left side of the screen is all the items in warsword. You will need to scroll down to the armor you would like to be used by all races or more then normal races. For this tutorial I will use 859 itm_dreadknight. On the bottom right side of the screen is a box with the word Factions (1): above it. Scroll down and we see that this armor is used by 33 - fac_kingdom_12 which is the dark elves. You can either add the kingdoms you want to also access the armor by check the box next to the kingdoms name or uncheck that box and allow everyone to use. Once you are done with the check boxes Click Update Item on the top right, this is important or it will not save your changes. When you go to exit, it will save your item_kinds and create a back up.
To get a list of factions in this mod (or whatever mod you are editing) on the top menu of the tool click select editor and choose factions, it will give you a list of all kingdoms with their faction number.
any questions just ask. I will keep checking to make sure to answer.
I love this mod but want to see the amazons in it and not just as raiders so I replaced the Nippon with my own amazon faction. While the module system gives complete control you can do a lot with this editor once you get the hang of it. This lets Nameless make the mod for everyone and me to tweak it for myself with changes that would not be popular for everyone else.