Enqueue Font Awesome styles

functions.php

<?php

function include_font_awesome() {
  wp_enqueue_style('font_awesome', '//netdna.bootstrapcdn.com/font-awesome/4.1.0/css/font-awesome.min.css');
}
/* When 'wp_enqueue_scripts' takes place, trigger this function */
add_action('wp_enqueue_scripts', 'include_font_awesome', 100);