to install these skins, replace your original materials folder with the one provided 
it can be found here

 C:\Program Files\Steam\steamapps\username\day of defeat source\dod

to un install go back to C:\Program Files\Steam\steamapps\username\day of defeat source\dod
and remove the player folder, no worries the game will automaticly replace the missing files with stock ones!

credits:Albanianshooter for requesting these