找到文件：
/template/default/common/header.htm
找到第125行：
<h2><!--{if !isset($_G['setting']['navlogos'][$mnid])}--><a title="$_G['setting']['bbname']" href="{if $_G['setting']['domain']['app']['default']} {$_G['scheme']}://{$_G['setting']['domain']['app']['default']}/{else}./{/if}">{$_G['style']['boardlogo']}</a><!--{else}- ->$_G['setting']['navlogos'][$mnid]<!--{/if}--></h2>
准备好你的广告代码，比如一个图片广告：(高度最好和你的logo一样，规定宽度和高度)
<a href="/forum-2-1.html" target="_blank" rel="noopener noreferrer"><img src="/images/70.gif" width="700" height="66" /></a>
或者按高度自适应：
<a href="/forum-2-1.html" target="_blank" rel="noopener noreferrer"><img src="/images/70.gif" height="66" /></a>
很简单，放到</h2>前面就可以了，最终效果：（红字是嵌进去的）
<h2><!--{if !isset($_G['setting']['navlogos'][$mnid])}--><a title="$_G['setting']['bbname']" href="{if $_G['setting']['domain']['app']['default']} {$_G['scheme']}://{$_G['setting']['domain']['app']['default']}/{else}./{/if}">{$_G['style']['boardlogo']}</a><!--{else}- ->$_G['setting']['navlogos'][$mnid]<!--{/if}--><a href="/forum-2-1.html" target="_blank" rel="noopener noreferrer"><img src="/images/70.gif" height="66" /></a></h2>