function for style your theme wordpress php

function register_styles() {
  wp_register_style( 'theme_styles', get_template_directory_uri() . '/styles/main_global.css' );
  wp_enqueue_style( 'theme_styles' );
}

wp_enqueue_style( 'slider', get_template_directory_uri() . '/css/slider.css',false,'1.1','all');