You could add a page and put a link to it in your menu by following this idea:
http://community.mybb.com/thread-116225.html
<?php
define('IN_MYBB', 1); require "./global.php";
add_breadcrumb("Rules", "rules.php");
eval("\$html = \"".$templates->get("rules.php")."\";");
output_page($html);
?>
<html>
<head>
<title>Rules</title>
{$headerinclude}
</head>
<body>
{$header}
<table border="0" cellspacing="1" cellpadding="4" class="tborder">
<tr>
<td class="thead"><span class="smalltext"><strong>Rules</strong></span></td>
</tr>
<tr>
<td class="trow1">
<p>#1 Rule number one</p>
<p>#2 Rule number two</p>
<p>#3 Rule number three</p>
<p>Just add more as you want them</p>
</td></tr></table>
{$footer}
</body>
</html>
Then add a link to it by going to Header Templates > Header
Find:
<ul class="menu top_links">
And under that add:
<li><a href="https://rservices-forums.com/rules.php" title="About our rules.">Rules</a></li>
Just play around with that and see if it help.