AAC Modern AAC - How to get Session Nickname.

[roronoaBenny]

Hello, before, sorry for the poor english, i'm a brazillian user.
Well, i'm trying to get Session Nickname in my custom Modern AAC template, but i still learning about web dev. So, im trying to do this:

Hello, <?php echo $_SESSION['nickname'];?>

Hello, <?php echo $_SESSION['nickname'];?>

Because i found this on account.php (page that shows user nickname).

<?php
$GLOBALS['characters'] = $characters;
$ide = new IDE;
try { $ide->loadInjections("account"); } catch(Exception $e) { error($e->getMessage()); }
    echo "<h2>Hello <a href='".url('profile/view/'.$_SESSION['nickname'])."'>".ucfirst($_SESSION['nickname'])."</a>!</h2>";

So, i ask to a friend and her say that i need to define the variable in index.tpl.
So, how can i do this?
Thanks u all