Ok, I will try to help you. Here is how to import it:
1. Open your map
2. Go to the import manager
3. Import DwarfForgeKeeper.BLP
4. Double-click it in the import manager
5. Check "Use custom path"
6. Enter this path instead of the normal one: Units\Human\Rifleman\Rifleman.blp
7. Click ok
8. Place the unit somewhere (or at least make sure you will be able to look at it closely)
9. Save your map
10. Test the game (ctrl + f9) and look closely at the rifleman, because the skin looks a lot like the normal rifleman.
Edit:
And btw, tell Pins at wc3sear.ch to mention the path of the skin =)