place into C: program files x86/steam/steamapps/common/team fortress 2/tf/custom
If you dont have a custom folder in 'tf' make one and place it there.

I personally have a separate folder for skins and sound mods that I dont want to make VPK, for organization purposes.
It shouldn't matter though.

If it doesn't work, try making it a VPK. Drag and drop the folder onto the vpk.exe and it'll 
provide you with a vpk file.

