First create your DataObjects and their ini files (the links ini file in particular if you want links displayed as select boxes). See Setting Up DB_DataObject.

<?php
require_once('DB/DataObject/FormBuilder.php');
//set up DB_DataObject config settings
$do =& DB_DataObject::factory('someTable');
$formBuilder =& DB_DataObject_FormBuilder::create($do);
$form =& $formBuilder->getForm();
if($form->validate()) {
  $form->process(array(&$formBuilder, 'processForm'), false);
  //this is optional, you can comment out this to make the form appear for editing again
  $form->freeze();
}
echo $form->toHtml();
?>