Installing a skin is really easy:

1.- DOWNLOAD THE SKIN FROM ICONSTREE
2.- UNZIP THE *.ZIP FILE WITH A PROGRAM LIKE WINZIP
3.- EXTRACT ALL FILES TO THE LOCATION OF YOUR WINAMP SKINS DIRECTORY
(Use to be c:\Program Files\winamp\skins)
BUT CREATING A NEW FOLDER WITH THE SKIN NAME
(ej: c:\Program Files\winamp\skins\APPLETREE)
THE FILES MUST BE UNZIPED ON THIS DIRECTORY¡
4.- RUN WINAMP
5.- CLICK ON THE PREFERENCES, OPTIONS, SKINS
6.- SELECT APPLETREE
7.- ENJOY