Where can I do this? This stuff is a lot harder than vb 3!
You can do it via css. Add something like this to the additional.css file:
.logo-image {
clear:both; float:none;
}
.doc_header {
text-align: center;
}
Or at the header template find the following code:
<div><a name="top" href="{vb:raw vboptions.forumhome}.php{vb:raw session.sessionurl_q}" class="logo-image"><img src="{vb:stylevar titleimage}" alt="{vb:rawphrase x_powered_by_vbulletin, {vb:raw vboptions.bbtitle}}" /></a></div>
And replace it with:
<div style="text-align:center;"><a name="top" href="{vb:raw vboptions.forumhome}.php{vb:raw session.sessionurl_q}"><img src="{vb:stylevar titleimage}" alt="{vb:rawphrase x_powered_by_vbulletin, {vb:raw vboptions.bbtitle}}" /></a></div>