How Include CSS file in Wordpress using Function

function_css.php

<?php


//includes all felxo_theme_file_css

function flexo_theme_file(){
    //inculde CSS file
    wp_register_style('bootstrap', get_template_directory_uri(). '/css/bootstrap.min.css', array(), '3.1.0',all);
    wp_register_style('fancybox', get_template_directory_uri(). '/css/fancybox/jquery.fancybox.css', array(), '3.1.0',all);
    wp_register_style('jcarousel', get_template_directory_uri(). '/css/jcarousel.css', array(), '3.1.0',all);
    wp_register_style('flexslider', get_template_directory_uri(). '/css/flexslider.css', array(), '3.1.0',all);
    wp_register_style('style', get_template_directory_uri(). '/css/style.css', array(), '3.1.0',all);
    wp_register_style('default', get_template_directory_uri(). '/skins/default.css', array(), '3.1.0',all);
    
    wp_enqueue_style('bootstrap');
    wp_enqueue_style('fancybox');
    wp_enqueue_style('jcarousel');
    wp_enqueue_style('flexslider');
    wp_enqueue_style('style');
    wp_enqueue_style('default');
 
}
add_action('wp_enqueue_scripts', 'flexo_theme_file');

?>