Now extract the zip file it to your JetAudio skins directory (usually: C:\Program Files\JetAudio\Skin )
On the default skin press the skin button in the top left orner (next to preferences). You should now be able to see a window displaying you the various skins you can select. To use my skin select XAudio Black and click okay. Give jetAudio a second to apply the skin and you should be done.
If that wasn't easy enough for you please feel free to ask again! Everybody starts from 0 somewhere ;-)