Questo codice deve stare in file functions.php:
function mktheme_scripts() {
wp_enqueue_style( 'bootstrap', get_template_directory_uri().'/assets/css/bootstrap.min.css');
wp_enqueue_style( 'style', get_template_directory_uri().'/style.css');
wp_enqueue_script('bootstrap', get_template_directory_uri().'/assets/js/bootstrap.bundle.min.js', array(), '1.0', true);
}
add_action('wp_enqueue_scripts', 'mktheme_scripts');