<link href="//netdna.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="form-group" id="pago-div">
<label for="amount" class="col-sm-3 control-label">Pago</label>
<div class="col-sm-3">
<input type="number" class="form-control" id="amount" name="amount">
</div>
<div class="col-sm-4">
<select id="f_pago" name="f_pago" class="form-control" required="">
<option>Efectivo</option>
<option>Tarjeta</option>
<option>Deposito</option>
<option>Cheque</option>
<option>Transferencia</option>
</select>
</div>
<div class="col-sm-2">
<button type="button" class="btn btn-default pay-add-button" id="click-me">
<span class="glyphicon glyphicon-plus"></span></button>
</div>
</div>