This gave me a good deal of trouble trying to import but I eventually got it to work. Works very well for a space type map.
4.5/5, simply because an install path isn't provided (I get why a specific one isn't provided to make it work with various tilesets, but it is a bit confusing imo)
For anyone trying to install this,
Terrainart\Outland\Outland_abyss.blp
Does work for a file path, if it's not working properly, make sure in the import manager that the skin is recognized as "Image/Texture" and not "Other". If it's "Other" try removing the import and reimporting it, and if that fails try re-downloading the file. Once installed and it's recognized as "Image/Texture" save your map and restart the WE (not just close map and reload)
The above is what it took me to get the skin to work, I hope it helps others use the skin.