Need help adding an action to registration and user form submit
You must implement hook_form_alter, like this:

function MODULENAME_form_alter(&amp;$form, $form_state, $form_id) {
  if ($form_id == 'user_register_form') { 
    $form['#submit'][] = 'name_of_callback_function';
  }
}


NOTE: You can also implement this hook in your theme. Remember to clear the cache.