Full code sample that shows how to embed the document signing flow using the docusign-node client: https://www.npmjs.com/package/docusign-node

embeddedSigning.js

// Install NPM package or download source
// https://www.npmjs.com/package/docusign-node
var docusign = require('docusign-node');

var async = require('async');
var assert = require('assert');
var fs = require('fs');

var integratorKey = "INTEGRATOR_KEY";
var email = "EMAIL";
var password = "PASSWORD";

async.waterfall([
  // Initialize DocuSign Object with Integratory Key and Desired Environment
  function init (next) {
    docusign.init(integratorKey, 'demo', 'false', function (error, response) {
      assert.ok(!error, 'Unexpected ' + error);
      var message = response.message;
      assert.strictEqual(message, 'successfully initialized');
      console.log(message);
      next(null);
    });
  },
  // Authenticate Yourself With DocuSign to Recieve an OAuth Token and BaseUrl
  function createClient(next) {
    docusign.createClient(email, password, function (error, response) {
      assert.ok(!response.error);
      docusign.client = response;
      next(null, docusign.client);
    });
  },
  // create and send envelope (signature request) 
  function createEnvelopeWithEmbeddedRecipient(client, next) {
    // configure the envelope's email subject and recipient(s)
    var emailSubject = "EMAIL_SUBJECT";
    var recipients = {};

    // add one signer to the envelope as well as one signHere tab located at
    // 100 pixels right and 150 pixels down from top left corner of document
    recipients.signers = [{
      'email': "RECIPIENT_EMAIL",
      'name': "RECIPIENT_NAME",
      'recipientId': 1,
      'clientUserId': 101, // |clientUserId| used to designate recipient as embedded      
      'tabs': {
        'signHereTabs': [{
          'xPosition': '100',
          'yPosition': '150',
          'documentId': '1',
          'pageNumber': '1'
        }]
      }
    }];

    // grab the document bytes of the document we want signed
    var document = fs.readFileSync("TEST.PDF");

    // add document information 
    var files = [{
      name: "test.pdf",
      extension: 'pdf',
      base64: new Buffer(document).toString('base64')
    }];

    // Send the envelope!
    client.envelopes.sendEnvelope(recipients, emailSubject, files, null, function (err, response) {
      assert.ok(!err);
      console.log('Envelope Information is: \n' + JSON.stringify(response) + "\n");
      next(null, client, response.envelopeId);
    });
  },
  // Request Recipient View (aka signing URL)
  function requestRecipientView(client, envelopeId, next) {
    // set the return url and authentication method params
    var returnUrl = 'http://www.docusign.com/devcenter';
    var authMethod = 'email';
    client.envelopes.getSignerView(null, "RECIPIENT_NAME", "RECIPIENT_EMAIL", 101, envelopeId, returnUrl, authMethod, function (error, response) {
      assert.ok(!error, 'Unexpected ' + error);
      console.log('\nNavigate to the following URL to sign the document: ' + response.url + '\n');          
      next(null);
    });
  }
]);