Add a Button within the content type overlay window for the url link
The page in your screen shot is a 'node add' page for a particular content type in your drupal site. Therefore the best way to add more elements there is to utilize hook_form_alter()

&lt;?php
function custom_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  if ($form_id == 'mynodetype_node_form') {
    dsm($form); // This function is available via Devel module. Here, it shows you the contents of $form in a structured manner, so that you know where to make the change to add a button.
    // Add code here to add button in the form etc.
  }
}
?&gt;


The above code snippet assumes your module name is custom and your content type name is mynodetype

To understand what code you need to write to add new form element (in your case a button), refer drupal form api - http://api.drupal.org/api/drupal/developer!topics!forms_api_reference.html/7