1. Installing and Enabling Gnome Shell
If you have not installed the Gnome Shell in Ubuntu 12.04, so do with this command from the terminal:
sudo apt-get install gnome-shell
wait until the installation is complete, then Exit and select a menu from the GNOME session and log back in to use Gnome Shell:
2. Installing Gnome Tweak Tool
Gnome Tweak Tool is an application that allows us to set the theme of Gnome Shell and extensions. To install it in Ubuntu 12.04, run this command from the terminal:
sudo apt-get install gnome-tweak-tool
3. Installing Gnome Shell Extensions
To be able to use Gnome Shell Extensions, you need to install Gnome Shell extensions by running this command sequence:
sudo add-apt-repository ppa: ppa: gnome3-team/gnome3
sudo add-apt-repository ppa: ricotz / testing
sudo apt-get update
sudo apt-get install gnome-shell-extensions
After installation is complete, reset the Gnome Shell in the following way: ALT + F2 -> type "r" (without the quotes) -> Enter gan leave comments ...........
Thanks To : Syahrullinuxer