The following code shows how to add form control add-on.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css"
href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.2.1/css/bootstrap.min.css">
</head><!--from ww w .ja va 2s . c o m-->
<body style='margin:30px'>
<div class="container-fluid">
<div class="row-fluid">
<div class="span8">
<form class="form-horizontal">
<div class="control-group">
<label class="control-label">Field 1</label>
<div class="controls">
<input type="text" />
</div>
</div>
<div class="control-group">
<label class="control-label">Field 2</label>
<div class="controls">
<div class="input-append">
<input type="text" /> <span class="add-on">%</span>
</div>
</div>
</div>
</form>
</div>
</div>
</div>
</body>
</html>