add style from wp function file code example

Example 1: function for style your theme wordpress

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

Example 2: how to add css file in wordpress

wp_enqueue_style( 'style', get_stylesheet_uri() );