When you first download a skin, you have 3 .zip files:
Open those archives with WinRAR and transfer the files in your archives to:
C:/Programme files/EA games/Battlfield 2/mods/bf2/
For example to install my spas12 I will open for first objects\_server and place this folder : "ussht\_spas12 in my objects_server in objects\_server>weapons>Handheld>"
Now do this for all archives.
If you want to play with them read my tutorial here to know how to!
Omg.. was it really that simple.. lol :D
Last time I tried to use custom skin (After I did so, I deleted them, since PB blocked me -.-' )
I edited the whole zip file (decompressed the original and the modified, copied files from the modified dir to the original and overwrited the files --> compressed it again to one zip file) :D