You just put it inside the <fieldset>. For example: <fieldset class="repeating_skills">
<div class='sheet-row'>
<div class='sheet-col' style='width:260px;'>
<select name="attr_SkillNameRank" class="dtype" value="4!" style='width:70px;'>
<option value="4!">d4</option>
<option value="6!">d6</option>
<option value="8!">d8</option>
<option value="10!">d10</option>
<option value="12!">d12</option>
<option value="12!+1">d12+1</option>
<option value="12!+2">d12+2</option>
<option value="12!+3">d12+3</option>
<option value="12!+4">d12+4</option>
</select>
<input type="text" name="attr_SkillName" value="Skill Name" style='width:152px;'/>
</div>
<div class='sheet-col' style='width:198px;'>
<span style='text-align:bottom; font-weight:bold;'>d</span><input type="number" name="attr_LinkedSkillNameAttScore" class="sheet-short" value="@{LinkedSkillNameAtt}" disabled="true" />
<label style='width:130px;'>
<select name="attr_LinkedSkillNameAtt" class="atype">
<option value="@{agility}">Agility</option>
<option value="@{smarts}">Smarts</option>
<option value="@{spirit}">Spirit</option>
<option value="@{strength}">Strength</option>
<option value="@{vigor}">Vigor</option>
</select> </label>
</div>
<div class='sheet-col' style='width:193px; text-align:center;'>
<input type="checkbox" name="attr_SkillEncumbrance" value="1" style="width:20px;" />
</div>
<div class='sheet-col' style='width:100px;'>
<input type="number" name="attr_SkillNameMod" class="sheet-short" value="0" />
<button type='roll' name='roll_SkillName' value='/em @{character_name} attempts to do something with @{SkillName} and rolls: [[{1d@{SkillNameRank}![@{SkillName}], 1d@{wilddie}![Wild Die]}kh1 + @{SkillNameMod}[Skill Modifiers] + @{ttmod}[Situational Modifiers] +(@{SkillEncumbrance}*@{encumbrance})[Encumbrance Penalty] - @{wounds}[Wounds] - @{fatigue}[Fatigue]]]!'></button>
<input type='hidden' name='attr_rollSkill' value='/em @{character_name} attempts to do something with @{SkillName} and rolls: [[{1d@{SkillNameRank}![@{SkillName}], 1d@{wilddie}![Wild Die]}kh1 + @{SkillNameMod}[Skill Modifiers] + @{ttmod}[Situational Modifiers] +(@{SkillEncumbrance}*@{encumbrance})[Encumbrance Penalty] - @{wounds}[Wounds] - @{fatigue}[Fatigue]]]!' />
</div>
</div>
</fieldset>