How to use profile2 profile type in custom form?
i Suggest to use hook_form_alter or hook_FORM_ID_form_alter to perform specific task of existing form of profile2.

function mymodule_form_alter(&amp;$form, $form_state, $form_id)  {
    switch ($form_id)  {
        case 'comment_form_id':
            $form['your_comment_form_name'] = array (
              '#type' =&gt; 'checkbox',
              '#title' =&gt; t ('Subscribe to replies to this comment'),
            );
            break;
        case 'user_register_form' :
           $form['actions']['submit']['#value'] = t('Submit');
           break;
     }
  }