To add css to wordpress is simple.. just use wp_enqueue_style
example :
wp_enqueue_style( 'wp-astti-style-bootstrap', plugins_url('lib/bootstrap-4/css/bootstrap.min.css', __FILE__));but the problem when use enqueue to boostrap css like that is the css will effect other element and make wordpress admin page look ugly.
Solution :
solution for this problem is wrapper.
