Np friend. I was there too

I am sure there are guide on hive that can explain you in detail. But I will try to help you
I suggest to first download the mod
Quenching Mod (Latest v1.9)
This will give your game all the folders which the original game should have
View attachment 400106
These folders are part of the models for all units/buildings/doodad in short all the things you see in the game they can be changed by adding the .mdx you want in the proper location
For these models you can read in my description where the .mdx model must be added
EXAMPLE:
- Warcraft III\retail\units\demon\felgaurd
Note: The .mdx files must have the name of the folder you copy them to.
- For example for me Warcraft III\retail\units\demon\felgaurd you will add the .mdx files with the name felguard and felguard_portrait
For more info see the guides on hive or search on youtube

. There are many sources that can help