How to Hide the "[ PR ] Premium WordPress Theme Snow Monkey" Meta Box

function plt_hide_snow_monkey_blocks_metaboxes() {
	$screen = get_current_screen();
	if ( !$screen ) {
		return;
	}

	//Hide the "[ PR ] Premium WordPress Theme Snow Monkey" meta box.
	remove_meta_box('snow-monkey-pr', $screen->id, 'normal');
}

add_action('add_meta_boxes', 'plt_hide_snow_monkey_blocks_metaboxes', 20);

Where do I put this code?