Here is a guide to install Gnome Tweak Tool on Ubuntu 13.04. You can install Gnome Tweak Tool using the Ubuntu Software Center.
GNOME Tweak Tool allows the adjustment of several advanced GNOME options that can’t be configured in gnome-control-center. This includes things like: fonts used in user interface elements and titlebar, font hinting and aliasing, alternative user interface themes, changes in window management behaviour, behaviour on laptop lid close, file manager desktop icons, icons in menus and buttons. Visit the Gnome Tweak Tool Homepage.
To install Gnome Tweak Tool click on the link below
Install Gnome Tweak Tool
When the software center is opened click on the Install button and enter your password to authenticate the installation. When Gnome Tweak Tool is installed you can close the software center, to start Gnome Tweak Tool press the SuperKey and type: gnome tweak tool