Quando não configurado, sua skin vem com o sub forum assim:

Vamos ao que interessa:
Acesse seu AdminCP- Look & Feel- clique na sua skin- Board Index- boardIndexTemplate
Procure por :
Código HTML:
<ol class='subforums'>
<foreach loop="subforums:$forum_data['subforums'] as $__id => $__data">
<if test="showSubForumsLit:|:$__data[3]"><li class='newposts'><else /><li></if><a href="{parse url="showforum={$__data[0]}" seotitle="{$__data[2]}" template="showforum" base="public"}" title='{$this->lang->words['go_to_forum']}'>{$__data[1]}</a></li>
</foreach>
</ol>
Substitua por:
Código HTML:
<ol class='subforums1'>
<foreach loop="subforums:$forum_data['subforums'] as $__id => $__data">
</ol>
<ol class='subforums'>
<if test="showSubForumsLit:|:$__data[3]">
<li class='newposts'>
<else />
<li>
</if>
<a href="{parse url="showforum={$__data[0]}" seotitle="{$__data[2]}" template="showforum" base="public"}" title='{$this->lang->words['go_to_forum']}'>{$__data[1]}</a>
</li>
</foreach>
</ol>
Salve e após isso va em:
Look & Feel- clique na sua skin- Forum View- forumIndexTemplate:
Procure por:
Código HTML:
<ol class='subforums'>
<foreach loop="sub_subforums:$forum_data['subforums'] as $__id => $__data">
<if test="showSubForumsLit:|:$__data[3]"><li class='newposts'><else /><li></if><a href="{parse url="showforum={$__data[0]}" seotitle="{$__data[2]}" template="showforum" base="public"}" title='{$this->lang->words['go_to_forum']}'>{$__data[1]}</a></li>
</foreach>
</ol>
Substitua por:
Código HTML:
<ol class='subforums1'>
<foreach loop="subforums:$forum_data['subforums'] as $__id => $__data">
</ol>
<ol class='subforums'>
<if test="showSubForumsLit:|:$__data[3]">
<li class='newposts'>
<else />
<li>
</if>
<a href="{parse url="showforum={$__data[0]}" seotitle="{$__data[2]}" template="showforum" base="public"}" title='{$this->lang->words['go_to_forum']}'>{$__data[1]}</a>
</li>
</foreach>
</ol>
Salve e após isso va em:
AdminCP/Look&Feel/skin/CSS/ipb_styles.css
Procure por:
Código PHP:
table.ipb_table ol.subforums {
padding-top: 6px;
margin-top: 5px;
}
table.ipb_table ol.subforums li {
background: transparent url(http://forum.sosinvision.com.br/public/style_images/clean/bullet_black.png) no-repeat 3px 4px;
color: #606060;
font-size: 0.85em;
padding: 0 4px 0 15px;
float: left;
}
Substitua por:
Código PHP:
.subforums {
float:left;
width:50%;
}
.subforums1 {
width:50%;
}
table.ipb_table ol.subforums {
margin-top:5px;
width:50%;
float: left;
}
table.ipb_table ol.subforums li {
background: transparent url(http://forum.sosinvision.com.br/public/style_images/clean/bullet_black.png) no-repeat 3px 4px;
color: #495457;
font-size: 0.85em;
padding: 0 4px 0 15px;
float: left;
}
table.ipb_table ol.subforums li.newposts {
background: transparent url(http://forum.sosinvision.com.br/public/style_images/clean/bullet_green.png) no-repeat 0px 0px;
color: #495457;
font-size: 0.85em;
padding: 0 4px 0 16px;
float: left;
Salve e após isso va em:
AdminCP/Look&Feel/skin/CSS/ipb_ie.css
e adicione isso:
Código PHP:
.subforums {
margin-top:16px;
}
.subforums1 {
margin-top:-16px;
}
Salve e veja como ficará seu Sub Forum.

Créditos:D4J
Fonte: SOSInvision