Install Gnome Shell in Ubuntu 11.10
Open the terminal and run the following command
sudo apt-get install gnome-shell
This will complete the installation.
Now you have to logout from the existing session if you want to login in to gnome shell desktop you need to select GNOME from the login Screen
Once you loggedin you should see similar to the following screen
You can improve your gnome shell desktop looks with nice themes
Once you have downloaded your theme extract them to their respective location.
Extract Gnome shell theme and GTK 3 theme to ~/.themes
Extract icon theme to ~/.icons
Extract custom font to ~/.fonts
Note: ~/ is a shorthand for your home folder. So ~/.themes is referring to the /home/username/.themes folder.