Fist you need to take the python script from here.
The script needs to be into the Blender script folder to be used.
Open the Blender 3D application, go to the File – User preferences search the word Screencast and enable the addon by check the checkbox.
To use this addon then go to the 3D View, hit Shift+Alt+C keys.
Another way is to press N key to see the right panel and then use the Start Display button.
See the next image:
