This is probably a stupid question about skins but i need help

i just downloaded the half elven ranger from the downloads section in the model section however instead of a model it's a skin and i'm wondering how to add a skin and portrait to the sylvannus windrunner model. any help would be greatly appreciated

There are two possibilities :
-you don't want to have two models for this unit in the same map, one with old skin and another with the new one. Just import the skin into your map and change the skin's path to Sylvanus Windrunner skin's path. The new skin will replace the old one. (NB: you'll then have to save your map, close the editor and relaunch it, else the editor won't be able to deal with the imported files).

-you want to have both skins in the same map. Then you'll have to:
*extract with war3viewer Sylvanus's and her portrait's model,
*convert them from mdx to mdl using Yogbul's file converter (both prgm can be found in the download section),
*edit with notepad the skin path in both mdl models to the new one (example: "Textures\HighElfRanger.blp"),
*change both model's names (example: Ranger.mdl and Ranger_portrait.mdl),
*save changes,
reconvert both mdl's to mdx using file converter,
*import both new models plus the skin in the map,
*change the skin's path to the one you entered in the mdl models,
*save,
*quit the editor and
*reopen the map.

you see the problem is that i dont know the path for the sylvannus windrunner file. I have a notebook file of all the tft paths but not for roc.

The path is : Units\Creeps\SylvanusWindrunner\SylvanusWindrunner.blp.

N.B.: I highly suggest that you get TheProphet's Warcraft 3 Viewer, it is not perfect and sometimes it does not show the same result as WorldEditor and WarcraftIII, but it is still a very usefull tool for a quick check of your work, for search of a models' or skins' path, or for the extraction of models and textures from the game's mpq. Can also convert between blp, tga, jpg and bmp.
Get Yogbul's file converter if you want to do simple edits of a model.
(The forums are full of threads explaining how to instal and use these programs.)