PSQ Need tutorial for transformation meshes

[alphafr]

I try hard to understand how  I am suppose to replace files so it only appear when transforming but I don't understand anything : I got 90 file to replace and half of them is body files (hand/feet/head...), I downloaded a mod for the wing and dunno if I have to use the containing file to replace, if I want to add a tail when transforming how do I do that? I am completelty lost and follow intruction doesn't help at all, i am not used to play around with .nif .tri files and even less with that many, also same for texture, the mod I downloaded doesn't contains any  for the wings so what??