Add AJAX popup multistep form
Here is the answer to my question by using the chaos tools:

// this creates the url that can be entered to reach this form
function ctools_ajax_sample_menu() {
  $items['ctools_ajax_sample/simple_form'] = array(
    'title' =&gt; 'Simple Form',
    'page callback' =&gt; 'regone_form',
    'access callback' =&gt; TRUE,
    'type' =&gt; MENU_CALLBACK
  );

  return $items;
}

function regone_form() {
  global $user;

  ctools_include('ajax');
  ctools_include('modal');

  // Add Ctools' JavaScript to the page.
  ctools_modal_add_js();

  $sample_style = array(
    'ctools-sample-style' =&gt; array(
      'modalSize' =&gt; array(
        'type' =&gt; 'fixed',
        'width' =&gt; 500,
        'height' =&gt; 400,
        'addWidth' =&gt; 20,
        'addHeight' =&gt; 15
      ),
      'modalOptions' =&gt; array(
        'opacity' =&gt; .5,
        'background-color' =&gt; '#246'
      ),
      'animation' =&gt; 'fadeIn',
      'modalTheme' =&gt; 'CToolsSampleModal',
      'throbber' =&gt; theme('image', array(
        'path' =&gt; ctools_image_path('ajax-loader.gif', 'ctools_ajax_sample'),
        'alt' =&gt; t('Loading...'),
        'title' =&gt; t('Loading')
      )),
    ),
  );

  drupal_add_js($sample_style, 'setting');

  ctools_add_js('ctools-ajax-sample', 'ctools_ajax_sample');
  ctools_add_css('ctools-ajax-sample', 'ctools_ajax_sample');

  $links = array();
  $links[] = ctools_modal_text_button(t('Wizard (custom alex modal)'), 'ctools_ajax_sample/nojs/animal', t('Pick an animal'), 'ctools-modal-ctools-sample-style');

  $output  = theme('item_list', array('items' =&gt; $links, 'title' =&gt; t('Actions')));

  // This deals with theming of the modal box.
  $output .= theme('ctools_ajax_sample_container', array('content' =&gt; '&lt;h1&gt;' . t('Sample Content') . '&lt;/h1&gt;'));

  return array('markup' =&gt; array('#markup' =&gt; $output));
}