Up till now, we have been using the default skin on the Harrier, VMA-233 (I think) in Honor of our previous illustrious leader, Bulldog. However, the process of getting and installing different skins for the Harrier is no different than for the Hornet or any other plane in the DCS World. Go into your saved games>DCS.openbeta>Liveries and create a new folder for the Harrier. I don't have any custom skins so I don't know what the correct format for the Harrier folder is but somebody in here must have that figured out by now.