How to add a heading at the top of node/add or node/edit?
If you mean to change the title of the page you can do this. This will make all node add form titles "Create new [content type]" instead of "Create [content type]".
It doesn't change the edit form because it doesn't make sense to put "new" in the title there because it is not new content, you are editing existing content.

Create a new custom module that implement this:

/**
 * Implements hook_form_BASE_FORM_ID_alter().
 */
function MODULE_NAME_form_node_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  // For the node add form.
  if (!$form['nid']['#value']) {
    // Add "new" to the page title.
    $node_types = node_type_get_names();
    drupal_set_title(t('Create new @type', array('@type' =&gt; $node_types[$form['#node']-&gt;type])));
  }
}