How do you edit a mesh from the game? Like say I want to tweak the shape of a pair of boots from the game. how would I go about doing this?

First you need Nifskope and a 3D Modelling program like Blender or 3DSMax (or Maya, or Hexagon or Milkshape etc.)

Then you load the NIF into Nifskope, and use File / Export / Export .OBJ.

OBJ is a file format any 3D-moddeling program can work with, it's a text file, so if need be you could even edit it by manually changing the vertex coordinates.

Load the .OBJ into your 3D-modelling program and edit it. (That's the hard part if you never used one, and the free Blender is even hard for those who have used other tools) When you're done save again as .OBJ.

Now load that NIF again into Nifskope, select the NiTriShape entry and import the .OBJ.
When everything is white and the new model didn't replace the old one you haven't selected a NiTriShape node.
When everything has the same color you might have forgotten to UV-map the modified model before exporting it.

Also check the Tangent spaces (Normals, Tangents and Binormals) under NiTriShapeData, you might to have to re-create them.
When you're done, save the NIF, and use the CK to add a new item, or save with the vanilla filename to replace the old one.

Where do I find these nifs? they are invisible.

They're in "Skyrim - Meshes.bsa". To extract stuff from the BSAs use the http://skyrim.nexusmods.com/downloads/file.php?id=1395 or http://newvegas.nexusmods.com/downloads/file.php?id=36901if you have one of the Fallouts.

and that was what I was missing...thank you very much! I really appreciate that.

AHHH This is what I needed to know also.

I tried loading a mesh into Nifskope but it said it failed to load. has anybody else encountered this problem?

No they have always worked for me. That sort of object is it?

Tread kidnapping but probably relevant, I have managed to export and mesh to 3d studio and imported it again and it work, some issues with textures but can solve that later.

However I have on serious roadblock, How do I add objects to the skeleton? Having an collar and want to add an simple object to the collar however I see no way of adding it, grouping it to the collar remove it from the collar so I wonder that function to use.

Its a piece of armor. I extracted it with the BSA Browser and every time I try to open it with Nifskope it says failed to load nif file.

Which version of Nifskope do you use?

You need the 1.1.0 branch for Skyrim support: http://sourceforge.net/projects/niftools/files/nifskope/1.1.0/

I Have 1.0.22 is the 1.1.0 a patch for skyrim support?

Bump.

Yep you need to use the 1.1 version if you want to open Skyrim Nifs -- http://www.niftools.org/ under the tools select Nifskope then on the next page select Download the Nifskope-RC then select the latest version to download.

I tried opening the OBJ file in Blender but it just gives me the default cube. Any idea what I did wrong?

Is it possible to edit the face/head part meshes in this way? I would like to tweak some of the facial feature preset meshes for a couple characters I have in mind.. I figured it would be possible, but I can't find the files anywhere with the BSA Browser. Any help would be very appreciated.