How to Hide GoSMTP Admin Menus

function plt_hide_gosmtp_menus() {
	//Hide "GoSMTP".
	remove_menu_page('gosmtp');
	//Hide "GoSMTP → Settings".
	remove_submenu_page('gosmtp', 'gosmtp');
	//Hide "GoSMTP → Test Mail".
	remove_submenu_page('gosmtp', 'gosmtp#test-mail');
	//Hide "GoSMTP → AI Abilities New!".
	remove_submenu_page('gosmtp', 'gosmtp-ai-abilities');
	//Hide "GoSMTP → Support".
	remove_submenu_page('gosmtp', 'gosmtp#support');
}

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

Where do I put this code?