How can I install themes from gnome-look.org?

[dihan91]

:confused:I am a beginner and dont know how to install those themes from gnome-look.org. please help me with the zip files, how can a zip file be a theme? can not intstall tar.gz icon files if I try this with the DESKTOP>[right button] CANGE DESKTOP BACKGROUND> THEME> INSTALL THEME> it shows invalid theme or etc error messages.

PLEase please help help