locate the last <!-- InstanceEndEditable --> tag that occurs befor the body tag.
just before it, add a script tag with that code in it:
<script language="language="javascript"">
WA_FilterAndPopulateSubList(groups_WAJA,MM_findObj ('UserCompany'),MM_findObj('GROUP_ID'),0,0,false,' : ');WA_setSelectionsInChildList(MM_findObj('GROUP_I D'),<?php echo $row_WADAusers['GROUP_ID']; ?>)
</script>
<!-- InstanceEndEditable -->