hide login & registration page from logged in users

I have login & registration pages which I wish to hide it or not display in my main menu. Can you please let me know how as I am pretty much a novice when it comes to coding. I am using zeeStyle theme from themeZee.

I found the following in my sidebar.php

<?php wp_list_categories(‘title_li=<h2 class=”widgettitle”>Categories</h2>’); ?>

<?php wp_list_pages(‘title_li=<h2 class=”widgettitle”>Pages</h2>’); ?>

• <h2 class=”widgettitle”><?php _e(‘Archives’, ‘themezee_lang’); ?></h2>

<?php wp_get_archives(); ?>

<?php endif; ?>
</div>

Please help and thanks in advance