UIbuilder: cant' seem to show the skin graphic

[battosa]

hi
i'm totaly new at this.
i searched on the forum and the uibuider doc but i don't find the answer

i try to change some stuff to some ui I use but UIBuilder don't show any graphic at all , juste some red box

what can i do to make them show up ?

thanks and sorry if this was already asked , could you at least point me to the answer ?