function add_my_css_and_my_js_files(){
        wp_enqueue_script('your-script-name', $this->urlpath  . '/your-script-filename.js', array('jquery'), '1.2.3', true);
        wp_enqueue_style( 'your-stylesheet-name', plugins_url('/css/new-style.css', __FILE__), false, '1.0.0', 'all');
    }
    add_action('wp_enqueue_scripts', "add_my_css_and_my_js_files");
 
 
Sample :
 
//register script and style

function add_aa_css_and_my_js_files(){
        wp_enqueue_style( 'style.css', plugins_url('/style.css', __FILE__), false, '1.0.0', 'all');
    }
    add_action('wp_enqueue_scripts', "add_aa_css_and_my_js_files");