How do I install themes for Gnome3 in Debian 7?

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http://superuser.com – I am trying to install the viva theme for my Debian install. I am having some issues. I am told to use the gnome tweak tool to select the theme. When I run the gnome tweak tool there is a yellow exclamation mark next to the theme selector portion. Through googling i've been told i'm missing extensions. When I try to add repo's detailed by various sources, then install the extensions mentioned, I am greeted with package not found messages. This is the theme i'm interested in- http://gnome-look.org/content/show.php/viva+3.10?content=156545 One of the troubles i'm having is alot of the posts I (HowTos)