I want to simply add a nif to another nif, to combine them into a new nif. In my case, I'm trying to add Hawk Feathers to an Iron War Axe. Why? Because tomahawk, that's why!

http://i46.photobucket.com/albums/f101/iwatson/axe_mod.jpg
OK, good, the feathers show up. But as with other newbs who have tried to add nifs to another nif, the Feathers aren't visible in the game, just the same old War Axe. There was some confusing talk about possibly needing to rename the new NiTriShape that is added, but I could never ascertain as to what I might name it. The "3" it has in that pic apparently was copied from the original nif, because it was also 3 in the original.
Any suggestions?