Problems with Mesh

[GladnxofxBakerStreet]

I am new to modding, but I want to learn how to work with meshes and things. Just simple edits to like saddles and things, using meshes from the game. Every tutorial that I've read that I can simply take the two nif files and paste one into the other. The meshes that I want to put together show up in nifskope just fine. I made textures and put them into creation kit: the mesh showed up there as well. I can put the textures on and have no problems with it up to that point; no warnings about nonfuctioning textures or anything. However, the problem is when I put it on the horse: suddenly, the skulls are no longer on the mesh in creation kit, and the saddle doesn't show up at all in game. I'm new with nifskope so I dunno if I have to merge things or something. I don't now what I'm doing wrong, but I'm trying to make a summonable custom horses mod and I would like more than to just retexture the saddles. I'm using the Imperial saddle, stag skull, werewolf totem skulls, and troll skull (with lower jaw removed so that it won't bounce). Please help... I am at a lost as to what I'm doing wrong.