I just start using crystalxp.
I download the icons and skins and PNGs,but i dont know how to use them.please anyone can teach me?

If you want, you can download Crystal XP Brico Pack !
It's very simply to use

PNG' files are for ObjectDock or Y'z Dock

i have download the software already.but i dont know where to put the icons.

which software?
if you mean ObjectDock, you just have to copy these icons in C:\Program Files\Stardock\ObjectDock

so that you can change the icons of the dock and choose the new ones.

topic title edited
try to explain your problem in it, please.