Possible Duplicate:
How do I get and install more themes, icons, and pointers?
Themes don't appear in gnome-tweak-tool
I'd download a theme and I want to apply it, I'm using Linux Ubuntu 12.4 system. and every time I tried to extract it I found a massage said : You don't have the right permissions to extract archives in the folder "file:///usr/share/themes"
I'm so new in Linux, so what can I do ???