font awesome example usage in CSS

#superfish-1-toggle::after {
content:"\f0c9";
font-family: "FontAwesome";
font-size: 24px;
font-weight: normal;
line-height: 1;
position: relative;
top:-12px;
text-decoration: none;
}

http://fontawesome.io/

add this to your .info file in your theme
stylesheets[all][] = css/font-awesome/css/font-awesome.css

and the font-awesome folder goes in the css folder.