Log User Into Web Account From App

I have an app, and in this app I want a user to login to a website from a textfield with in the app and then some data from that users account on the website can be displayed in the app. I have taken a look at this Ray Wenderlich tutorial, http://ift.tt/wU3AHD. And it has given me a good start, but this tutorial is a bit out of date I found an updated project that does the same thing here. http://ift.tt/1HVutFB but I am confused about how to put in my url for the page I want to log into and then how to find the username and password fields on that page?

So I am wondering how to log in a user to a website from my app, and just the next step.

Thanks for the help in advance.