Edit your footer template
Find:
Code:
<div align="center">
<div class="smallfont" align="center">
<!-- Do not remove this copyright notice -->
$vbphrase[powered_by_vbulletin]
<!-- Do not remove this copyright notice -->
</div>
<div class="smallfont" align="center">
<!-- Do not remove $cronimage or your scheduled tasks will cease to function -->
$cronimage
<!-- Do not remove $cronimage or your scheduled tasks will cease to function -->
$vboptions[copyrighttext]
</div>
</div>
Add what you want under that.