Once done, open the /ViewModels/TokenRequestViewModel.cs file and perform the following changes:

[...]

#region Properties
public string grant_type { get; set; }
public string client_id { get; set; }
public string client_secret { get; set; }
public string username { get; set; }
public string password { get; set; }
public string refresh_token { get; set; }
#endregion

[...]

This property will be used by our client to send the refresh token back to the web server--with the corresponding grant_type--to receive a new access token.