I think some of theme in Ubuntu is very beautifull and very nice so I go to this site http://www.gnome-look.org and download some beautifull unbuntu theme and I want installl it in debian sarge

so I unpack themes and put them in this directory
/usr/share/theme

but after this I can not use new theme for my debian and that is not impossible
please help what I must do
for install ubuntu theme in debian