Bootstrap is a library to be used on the client, regardless of whether you are using Node or not. The standard template included illustrates well:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- As três tags meta acima *precisam* serem as primeiras na head; qualquer outro conteúdo deve vir *depois* dessas tags -->
<title>Modelo do tutorial do Bootstrap</title>
<!-- Bootstrap -->
<link href="css/bootstrap.min.css" rel="stylesheet">
<!-- shim HTML5 and Respond.js para o suporte do IE8 a elementos HTML5 e media queries -->
<!-- ATENÇÃO: Respond.js não funciona se você visualizar a página pelo file:// -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script><scriptsrc="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
<![endif]-->
</head>
<body>
<h1>Hello, world!</h1>
<!-- jQuery (necessário para os plugins Javascript do Bootstrap) -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script><!--Incluatodosospluginscompilados(abaixo),ouincluaumporumquandofornecessário--><scriptsrc="js/bootstrap.min.js"></script>
</body>
</html>
Note that this example assumes that the bootstrap.min.css file is inside the css folder, and that folder is in the same directory as this HTML file. Adjust according to your case (search if you need to find out where your file went). The same thing with the bootstrap.js file.