So if u wanna install skin do the following:
get the file with skin.
Now get P2K tools and open it. (If u have not installed P2K drivers do it first).
On P2K mode click on refresh.
U will get file list of ur fone.
Then click at /a/
Now it is time to upload the files for skin.
Now u need to upload spcolor.sch and mma_ucp in the folder /a/mobile/system.
Then the images in /a/mobile.
U have the names of folder specified in the skin u downloaded so u can use ur logic to upload files in correct folder.
Now u get skin installed.