Default Widgets Unregister

Hi there,

I am trying to get rid of some of the default widgets that come with my theme …like on the sidebar. I found the following code:

add_action( 'widgets_init', 'my_unregister_widgets' );

function my_unregister_widgets() {
	unregister_widget( 'WP_Widget_Pages' );
	unregister_widget( 'WP_Widget_Calendar' );
	unregister_widget( 'WP_Widget_Archives' );
	unregister_widget( 'WP_Widget_Links' );
	unregister_widget( 'WP_Widget_Categories' );
	unregister_widget( 'WP_Widget_Recent_Posts' );
	unregister_widget( 'WP_Widget_Search' );
	unregister_widget( 'WP_Widget_Tag_Cloud' );
}

But I have no clue what to do it? Should I insert it to my functions.php and if yes, where exactly? Do I have add any code or opening tags for php , etc?

Sorry to ask these types of question. I have no php background, just trying to desperately put up my blog.

regards
thanks,

Vicnent