PowerBI Embedded Create Report based on Dataset

[nd1022]

I am trying to create PowerBI report using PowerBI Embedded SDK , I have followed below github article.

https://github.com/Microsoft/PowerBI-JavaScript/wiki/Create%5CEdit-Report-in-Embed-View

Could you please elaborate on how to generate the access token?

Accesstoken generated using below code is not valid and it return 403 error on PowerBI.createreport function. 

using Microsoft.PowerBI.Security;

// rlsUsername and roles are optional
string scopes = "Dataset.Read Workspace.Report.Create";
PowerBIToken embedToken = PowerBIToken.CreateReportEmbedTokenForCreation(workspaceCollectionName, workspaceId, datasetId, null, null, scopes);

var token = embedToken.Generate("{access key}");

Also where to get the Access Key as show in last line of above code?

Thank You