How make wp_nav() with my css?

First step is to register the name (or names) for your menus. In your example, top-nav seems appropriate.

function vd_register_menu() {
  register_nav_menu('top-nav',__( 'Top Nav Menu' ));
}
add_action( 'init', 'vd_register_menu' );

This will allow you to build your menu items in the WP admin under Appearance > Menus.

To display your menu on the site, simply call the wp_nav_menu() function where you wish to print the code.

<?php wp_nav_menu( array( 'theme_location' => 'top-nav' ) ); ?>

Full documentation available via WP Codex: https://codex.wordpress.org/Navigation_Menus