This is the base example of the Redactor installation. Please, read more in the documentation article.
<!DOCTYPE html>
<html>
<head>
<title>Redactor</title>
<meta charset="utf-8">
<!--css -->
<link rel="stylesheet" href="/your-folder/redactor.css" />
</head>
<body>
<textarea id="content"></textarea>
<!-- js -->
<script src="/your-folder/redactor.js"></script>
<!-- call -->
<script>
$R('#content');
</script>
</body>
</html>