open xs++, connect the phone, navigate to fsx and let it open. Navigate to: tpa/system/multimedia/mp/skin

You will see in the skin section probably a white and an orange skin folder... what you want to do first is create more folders in the skin folder.
1) Click on Skin,
2) Create Dir (ex. everchanging)
3) Create another Folder... repeat depending on how many skins you have
4) You wont see them in their until you shutdown xs++, so shutdown, remove battery. and reconnect and navigate to tpa/system/multimedia/mp/skin. Now you will see the new dir you created before.
5) Just drag and drop the files into the empty directories.
6) Shutdown and disconnect.. should be good to go