xili-language plugin – trying to add flags but it doesn't work

Hi,
I’m trying to add flags to my website – unfortunately it won’t work. I went to xili’s websites and found the code to add to the css to show the flags… I added the code below, but I assume I have to make some changes to the php to, but I don’t know which ones??
Right now no language shows on the site, not even as a text-list…
I am a newbie to css/php so please explain what I have to do.
Thanks.
J

This is the code in css:

License: GNU General Public License
License URI: license.txt
*/

/* some few modifications for xili-language list */
ul.xililanguagelist {list-style: none !important ; margin-left:0 !important ;}

/* example in header menu if filter xiliml_infunc_language_list is on*/

ul.menu li.lang-en_us a {background: transparent url(images/flags/en_us.png) no-repeat center 13px;}
ul.menu li.lang-de_de a {background: transparent url(images/flags/de_de.png) no-repeat center 13px;}
ul.menu li.lang-es_es a {background: transparent url(images/flags/es_es.png) no-repeat center 13px;}

li.lang-en_us:hover > a {background: #333 url(images/flags/en_us.png) no-repeat center 13px !important;}
li.lang-de_de:hover > a {background: #333 url(images/flags/de_de.png) no-repeat center 13px !important;}
li.lang-es_es:hover > a {background: #333 url(images/flags/es_es.png) no-repeat center 13px !important;}

ul.menu li.lang-en_us, ul.menu li.lang-de_de, ul.menu li.lang-es_es {text-indent:-9999px; width:18px;}

/*
CSS Reset
*/