I've downloaded some files from gnome-look.org and would like to try them out. If I go to Applications --> Preferences --> Theme, the theme preferences windows opens which offers me the available themes plus an "Install Theme" button, which I used to install th following:

lila-backgrounds-0.3.4.tar.bz2
lila-gnome-0.6.3.tar.bz2
lila-gtk-0.5.5.tar.bz2

However, none of this appears to be added to my available themes. I've restarted Gnome (just in case) but with no result.

If I go to Theme Preferences --> Theme Details --> Go To Theme Folder, I am taken to a .theme folder in my /home directory which has several folders related to the theme I just installed (Lila, lila-backgrounds, lila-gnome, lila-gtk)

How do I install a new theme so that I can actually use it?

generally you just extract the themes ( use file-roller or the command line) and point the theme manager to the extracted directory.

what i have seen many times is that you will just point the gnome theme manager to the compressed archive and it will decompress itself and install the theme automatically...

... which is exactly what I've done...??