代码示例如下，请根据自己的需要修改，将代码添加到当前激活主题的 functions.php：

/**
 * 添加图片广告到B2主题页眉下方
 * https://www.wpdaxue.com/docs/b2/b2-dev/banner-below-header
 */
add_action('b2_content_before', function(){
    echo '<div class="dddd ads-after-header">
            <div class="wrapper">
                    <a target="_blank" href="https://www.wpdaxue.com/go/joowp">
                            <img width="598" height="80" alt="点击查看广告位详情" src="https://www.wpdaxue.com/img/2022/07/joowp.png" >
                    </a>
                    <a target="_blank" href="https://www.wpdaxue.com/wordpress-templates">
                            <img width="598" height="80" alt="外贸建站，就用成品站模板" src="https://www.wpdaxue.com/img/2022/08/mubanjz.png" >
                    </a>
            </div>
    </div>';
});

样式代码参考如下，根据自己的需要调整，可以添加到主题的 style.css：

.vips .ads-after-header {
    display: none;
}
.ads-after-header {
    margin-bottom: 16px;
}
.ads-after-header a {
    display: inline-block;
    width: 49.8%;
    max-width: 598px;
}
.ads-after-header a:first-child {
    margin-right: 0.4%;
}
.ads-after-content {
    margin-top: 16px;
}
.post-style-5 .ads-after-header {
    display: none;
}
@media screen and (max-width: 768px){
    .ads-after-header {
        margin-bottom: 4px;
    }
    .ads-after-header a {
        width: 100%;
        max-width: 768px;
        margin-bottom: 2px;
    }
    .ads-after-header a:first-child {
        margin-right: 0;
    }
}