Interested to insert a widget into a page

Hi, I came across this neat article; which seemed like the best way to insert widgets into pages/posts (interesting stuff!):

http://digwp.com/2010/04/call-widget-with-shortcode/

However I have no idea where to enter this code into my functions.php file. I have a safe copy backed-up… But really like I said, I have no idea where to start. Would anyone be able to assist me on this? Many thanks.