How to Hide the "LIQUID SPEECH BALLOON" Admin Menu

function plt_hide_liquid_speech_balloon_menus() {
	//Hide the "Settings → LIQUID SPEECH BALLOON" menu.
	remove_submenu_page('options-general.php', 'liquid-speech-balloon');
}

add_action('admin_menu', 'plt_hide_liquid_speech_balloon_menus', 11);

Where do I put this code?