Lets say I downloaded a weapon model resource and I want to use it. However it contains a mesh and lots of texture like *something*_n.dds.
How do I apply it to my weapon then? I only know how to change the weapon model, and that uses up the mesh. Then where do the textures go?
The path to the textures is defined in the nif files. You need to use the same folder structure in Data\Textures\ the creator of the Nif file used. Usually the textures should already be in the correct sub folders in the ZIP file, and you just need to copy everything into the data folder.
You can use tools like Nifskope to change where the NIF looks for the texture, when you want all files of your mod to be in the same sub folder, but you don't need to.
If the weapon came with a very big texture file, this is most likely the first person variant, much more detailed because the player sees it very close. Using it is optional but advisable:
1. Create a new Texture Set (in the Miscellaneous tree) using the large name.dds file as "diffuse map" the "name_n.dds" file as Normal/Gloss map, the name_m.dds file as Environment Mask, and the "name_e.dds" file as Environment Map
2. Make a new static using the weapon as NIF file, and in the model menu the new texture set you created as override for all textures (unless the readme of the model resource says otherwise)
3. This new static ist then used by the weapon as "1st person Model Object"
Texture sets can also be used to retexture objects without having to add a modified variant to your mod. An example is the Brotherhood Scribe Robe with its retextured Elder and Bright Brotherhood variants, they all use the same model, but the later two use different dexture sets.