You definitely have to load it in the model. Your model has to extend JModelAdmin and then the getForm
function has to load the form
public function getForm($data = array(), $loadData = true) {
// Get the form.
JForm::addFormPath(JPATH_COMPONENT_ADMINISTRATOR . '/models/forms');
JForm::addFieldPath(JPATH_COMPONENT_ADMINISTRATOR . '/models/fields');
$form = $this->loadForm('com_dpattachments.attachment', 'attachment', array('control' => 'jform', 'load_data' => $loadData));
if (empty($form)) {
return false;
}
....
}
I'm using the same approach in my DPAttachments component, it is for Joomla 3.1 but the main code, to use the same model and form on the front and back, should also run on Joomla 2.5. Here is the link to the getForm function https://github.com/Digital-Peak/DPAttachments/blob/master/com_dpattachments/admin/models/attachment.php#L102