Default game controler setup

Hello, I am using by default the player controller…and I am going through a tutorial now to set up a hud that is toggled off and on…in this tutorial he sets up a new game controller so that he is able to add items to the controllers blueprint…am I able to add items to the PlayerConrollers blueprint as is and if so where do I find it … if not when I go in to Maps & Modes to change the playerController Class it is greyed out…how would I like the new controller if need be?

Video I am going through: Unreal Engine 4 Tutorial – Toggle Widgets - YouTube

You need to create a new Game Mode and Player Controller.

Thank you @revoverdrive that worked for me perfectly!