Access to HBO GO and/or HBO Now and Showtime Anytime with Uverse?

I have Uverse 300 with HBO and Showtime. I subscribe to internet and TV through Uverse. Does anyone know if I can access HBO Go and HBO Now through their apps or via  Apple TV? If so, how do I login? It asks for my internet provider username and password which I've provided (xxxxxxxx@att.net + password) but it says they are incorrect. I know it's not incorrect because I logged into my Uverse account online using the same user/PW.

Thanks!