Um... that's not a skin, that's an own model, or what did you want to do?
![Thinking face :thinking: 🤔](https://cdn.jsdelivr.net/joypixels/assets/7.0/png/unicode/64/1f914.png)
Import the model, remove the "war3mapimported/" in front of the textures and then assign the model via "Art - Model File" in the Object Editor
either to your own unit or to the existing necromancer.
Did I answer your question with that?