Need help making mesh replacement work ingame

[kuunkulta]

So long story short, I'm new when it comes to editing meshes and I need a little help learning this stuff. So what I'm trying to do here, is make a mesh I edited in 3dsMax to work in Skyrim. I took the original femalehead.nif, opened it in 3dsmax, edited what I wanted, exported it to .nif format and opened it in nifskope. I made sure bones are in right places and have the right names. But what do I do now? The head doesn't show in-game and I honestly have no idea what I should do at this point. So, little help?

 

I attached the new mesh to this post but so you can check if I've done something wrong, but in order to learn the correct process, I need advice on what I did wrong and what I should do to make the mesh work. (UV map might be upside down too but that's minor concern atm)