How do I Add links in NAV BAR (vB 3.0.7)

[EchoZA]

I have search around but find it a little confusing (was just getting good with XMB and then moved over to vBulletin 3.0.7)

I used to have a link on my old forum, as follows:-

<!-- seed bank link -->
<a href="#" onclick="Popup(\'http://treatingyourself.com/cgi-bin/online/storepro.php\', \'Window\', 700, 450);">Seed Bank</a>
<!-- / seed bank link -->

and would like to know what is the best and simplest way to incorporate that into my nav bar on vBulletin 3.0.7?

Thanks,

EchoZA