Where would I go about editing a already made framework like the full html

So I have a prepaid site and in the main.php it has:

<div id="outer">


    if (!$simple)



        $this->widget('zii.widgets.CBreadcrumbs', array(





?><!-- breadcrumbs -->

<?php echo $content; ?>

Where would I edit the $content; ??

This is from Yii1.

The $content variable will be replaced by what the current action returns.