Fire and Ice, that does not work unless you do a registry modification.
The problem is eithor caused by broken models, incorrect pathing or you not folowing import tutorials.
You have to import the model and rename the skins to be the right path that the model needs. Then you need to save your map. Then close your map and WE and WC3. Then reopen your map with WE. The model will now be visable. If it is not visable, you eithor did not folow the above or the model is broken.