I'm normally the one asking this questions myself but maybe I can help you on this one.
In your Style Manager open
Navigation / Breadcrumb Templates for the skin you are using. Now open the
NAVBAR template and look for this:
Code:
<!-- nav buttons bar -->
This area contains the links in your navbar. To add something find where you want to add it and add something like this:
Code:
<td class="vbmenu_control"><a href="faq.php?$session[sessionurl]" accesskey="5">$vbphrase[faq]</a></td>
<td class="vbmenu_control"><a href="payments.php?$session[sessionurl]">Subscriptions(or whatever you wish to name the link)</a></td>
<td class="vbmenu_control"><ahref="memberlist.php?$session[sessionurl]">$vbphrase[members_list]</a></td>
The red text would be the link to your Subscriptions system and it would be places between the link to your FAQ and your Memberlist.
Hope this helps!