Problems with OAuth on node.js

I am trying to get OAuth to work on node.js. I found this in the documentation of node-oauth:

var OAuth= require('oauth').OAuth;var oa = new OAuth(requestUrl,accessUrl,consumerKey,consumerSecret,"1.0A",responseUrl,"HMAC-SHA1");

The next step in the official tutorial says:

"Then get hold of a valid access token + access token secret as per the normal channels"

What are these "normal channels"?

I know that the user has to authenticate somehow on the "vendor" site and that by some way a response url is called, but I can't find a description how to implement this. Can someone enlighten me?