You will need to link to the cms_style.css file. For example, open the index.php in the admin folder and this line of code:
<link rel="stylesheet" type="text/css" href="../css/cms_styles.css"/>
under this line of code:
<!-- InstanceBeginEditable name="head" -->
so you have:
<!-- InstanceBeginEditable name="head" -->
<link rel="stylesheet" type="text/css" href="../css/cms_styles.css"/>
This will include the cms_style.css file on your index page because the cms_style.css is where you have your class definitions. And if you click on the home page of CMS, you should see the styles shown. similarly if you want those styles to show on other pages you will need to add this line of code:
<link rel="stylesheet" type="text/css" href="../css/cms_styles.css"/>
to those pages as well.