It all depends on what you want to add skins to. If you are wanting to add skins to some of the aircraft, it is not possible because there is no void file. I know you know how to skin because we have seen some of your skins previously. It is simply a case of finding the relevant aircraft folder and dropping your skin file into it. Now, if you are using W7, as you said, sometimes the skins files will not show up once you have dropped them in. They will be hiding in "Compatibility Files" at the top of the screen. If this happens, click on the tab for compatibilty files and select share or cut/paste once you see the skin you made. This will put the skin back into the main aircraft folder and then it will be available for selection in the game.
Hope that clears it up for you felon. Let me know if there are any issues.
~S~