Multiple Select textbox HTML - Bootstrap 3

bagaimana cara mengubah textbox select multiple ini ?

 // form

<!--catatan mutu-->
								<?php
								include "config.php";
								error_reporting(0);
								$hasil=mysql_query("SELECT * FROM catatan_mutu");
							  	?>
								<div class="form-group">
									<label class="col-md-3 control-label" for="catatan">Catatan</label>
									<div class="col-md-6">
									<select class="form-control" id="multi" name="catatan[]" multiple>

							  			<?php
							    		while ($baris = mysql_fetch_array($hasil)){
							      		?>
							      		<option value="<?php echo $baris[judul];?>"><?php echo $baris[judul];?></option>
							      		<?php
							    		}
							     		?>
									</select>
									</div>
								</div>

 JQUERY
!function ($) {
			$(document).on("click","ul.nav li.parent > a > span.icon", function(){
				$(this).find('em:first').toggleClass("glyphicon-minus");
			});
			$(".sidebar span.icon").find('em:first').addClass("glyphicon-plus");
		}(window.jQuery);

		$(window).on('resize', function () {
		  if ($(window).width() > 768) $('#sidebar-collapse').collapse('show')
		})
		$(window).on('resize', function () {
		  if ($(window).width() <= 767) $('#sidebar-collapse').collapse('hide')
		})