How to Hide the "WaveSurfer-WP" Admin Menu

function plt_hide_wavesurfer_wp_menus() {
	//Hide the "Settings → WaveSurfer-WP" menu.
	remove_submenu_page('options-general.php', 'wavesurfer-wp');
}

add_action('admin_menu', 'plt_hide_wavesurfer_wp_menus', 1000);

Where do I put this code?