Attempting to create my first body mod, it appears in game but is not attached to the head!

[ProfMaxHammer]

So I'll preface this by saying I'm a complete beginner to modding, blender etc...

 

I've been trying to remodel Ciri's body but in game it just appears as a static model as it does in Blender. Her head spawns in the right place but the body stays in the same place while you walk around as a floating head.

 

As far as I know the only thing I'm changing is her mesh. I guess there is something I need to do so the body can animate?

 

Any enlightenment would be greatly appreciated!