In most cases, you don't need to change the path of the actual model file. Thus, keeping war3mapImported\Aragorn.mdx doesn't matter.
At the Aragorn Model submission in the models section you can however see a table labelled
"Textures"
This table contains 3 texturefiles. 2 are marked in red. This means that these 2 texturefiles are custom textures that are required for the model to work. So what you need to do is import
Aragorn.blp
Narsil.blp
and then change the path of the .blp texturefiles into the path mentioned in that table. In this specific case:
Textures\Aragorn.blp
Textures\Narsil.blp
Finally, save your map and restart WE so you refresh the textures. Now the model should show up.