Yii form submition with CActiveForm

i just need to do a registration form, i'm battling with completing this task with CActiveForm. Basically its just inserting a new db record on form submit. This is what i have,

MyView

<!--begin a form-->
<?php $form = $this->beginWidget('CActiveForm', array(
   'id'=>'user-registration-form',
   'enableAjaxValidation'=>true,
   'enableClientValidation'=>true,
   'focus'=>array($model,'firstName'),
)); ?>

<!--error handling-->
<?php echo $form->errorSummary($model); ?>

<div class="row">
   <?php echo $form->labelEx($model,'firstName'); ?>
   <?php echo $form->textField($model,'firstName'); ?>
   <?php echo $form->error($model,'firstName'); ?>
</div>
<div class="row">
   <?php echo $form->labelEx($model,'lastName'); ?>
   <?php echo $form->textField($model,'lastName'); ?>
   <?php echo $form->error($model,'lastName'); ?>
</div>
<div class="row">
   <?php echo $form->labelEx($model,'age'); ?>
   <?php echo $form->textField($model,'age'); ?>
   <?php echo $form->error($model,'age'); ?>
</div>

<?php $this->endWidget(); ?>
<!--end a form-->

My Controller that renders the above view, this where i'm stuck,

I also created a model called User(haven't done any code in it, default)

class RegisterController extends Controller
{
   public function actionIndex()
      {
        $model = User::
        $this->render('index', array('model'=>$model));
     }
}

From my research i found there is something like, jst dnt know how to use it link

$post=new Post;
$post->title='sample post';
$post->content='post body content';
$post->save();

Thanks in advance