To add a link to Open Review Policy page in the plugin at the end of the policies section of the journal's About page:

added to OpenReviewPlugin.Inc.php

in the register() function

HookRegistry::register('Templates::About::Index::Policies', array(&$this, 'addOpenReviewPolicyLinks'));

function addOpenReviewPolicyLinks($hookName, $args) {
...
$output .= '<li>» <a href="'. $templateMgr->smartyUrl(array('page' => 'openreview', 'op'=>'openReviewPolicy'), $templateMgr) .'">';
...
}

the value of the "op" argument (openReviewPolicy) is the name of the function in OpenReviewHandler.Inc.php to invoke on launching the page whose name matches the value of the "page" argument (openreview).