Adding search functionality in select options using Bootstrap

    <link href="//netdna.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet">
    <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.6.3/css/bootstrap-select.min.css" />

<select class="selectpicker" data-show-subtext="true" data-live-search="true">
<option data-tokens="name">name</option>
<option data-tokens="family">family</option>
</select>
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
  <script src="//cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.6.3/js/bootstrap-select.min.js"></script>

Multi Selection Form and searchable

$(function() {
	$('.selectpicker').selectpicker();
});
<!DOCTYPE html>
<html>
<head>
	<title></title>
	<script type="text/javascript" src="js/script.js"></script>
	<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
	<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
	<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet" />
	<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/js/bootstrap-select.min.js"></script>
	<link href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/css/bootstrap-select.min.css" rel="stylesheet" />
	<script src="http://cdn.rawgit.com/davidstutz/bootstrap-multiselect/master/dist/js/bootstrap-multiselect.js"type="text/javascript"></script>
	<link href="http://cdn.rawgit.com/davidstutz/bootstrap-multiselect/master/dist/css/bootstrap-multiselect.css"rel="stylesheet" type="text/css" />
	<script>
		$(function () {
			$('#lstFruits').multiselect({
				includeSelectAllOption: true
			});
			$('#btnSelected').click(function () {
				var selected = $("#lstFruits option:selected");
				var message = "";
				selected.each(function () {
					message += $(this).text() + " " + $(this).val() + "\n";
				});
			});
		});
	</script>
</head>
<body>
<div class="container">
	<div class="row">
		<div class="col-xs-12">
			<div class="box">
				<div class="box-body">
					<form action="#" method="POST">
						<div class="form-group row">
							<div class="col-sm-10">
								<select class="form-control selectpicker" id="select-country lstFruits" multiple="multiple" data-live-search="true">
									<option data-tokens="china">China</option>
									<option data-tokens="malayasia">Malayasia</option>
									<option data-tokens="singapore">Singapore</option>
								</select>
							</div>
						</div>
					</form>
				</div>
			</div>
		</div>
	</div>
</div>
</body>
</html>

To get a search functionality you must set the data-tokens attribute for each options. Here is your code after adding it. Let me know if you need additional help.

$(function() {
  $('.selectpicker').selectpicker();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/js/bootstrap-select.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/css/bootstrap-select.min.css" rel="stylesheet" />




<div class="container">

  <div class="row">
    <div class="col-xs-12">
      <div class="box">
        <!-- /.box-header -->
        <div class="box-body">
          <form>
            <div class="form-group row">
              <label for="" class="col-sm-2 form-control-label">Country</label>
              <div class="col-sm-10">
                <select class="form-control selectpicker" id="select-country" data-live-search="true">
                <option data-tokens="china">China</option>
  <option data-tokens="malayasia">Malayasia</option>
  <option data-tokens="singapore">Singapore</option>
                </select>

              </div>
            </div>
          </form>
        </div>
        <!-- /.box-body -->
      </div>
      <!-- /.box -->
    </div>
    <!-- /.col -->
  </div>
  <!-- /.row -->
</div>
<!-- /.container -->