Hey there, If you're trying to create a new humanoid NPC, it is best to adjust the rig to fit the existing game rig (by renaming bones) or to rerig the mesh entirely. This way existing animations would be able to work with it, though compatibility is largely dependent on similar shape. After that it a process of exporting the rerigged reskinned meshes for the head as HeadParts, and skin/clothing as ArmorAddons for them to be usable for the NPC. Exporting can be done with niftools created for either 3ds max (officially created workflow) or maya/blender, more can be found about this on the internet. Only recently have I been able to dabble into this topic in fallout 4 with limited success, by no means do I have much experience with this as I'm still learning about it, I'm just trying to add additional input. Best of luck!