You can add it right below the other logout code:
<?php require_once('../webassist/mysqli/authentication.php'); ?>
<?php
if ("" == "") {
$LogOut = new WA_MySQLi_Auth();
$LogOut->Action = "logout";
$LogOut->Name = "signin";
$LogOut->execute();
}
@session_start();
session_destroy();
?>
<?php include("../partials/header.php"); ?>
<div class="full-content">
<div class="logout">