I am still very new to using Power Apps. There is a hiring tool template that looks ideal but I see no way to modify either the company departments or employees. How do I get to the underlying data to update those records?

I am still very new to using Power Apps. There is a hiring tool template that looks ideal but I see no way to modify either the company departments or employees. How do I get to the underlying data to update those records?
I've seen online tutorials, and they show a step where the question is asked where to store the data. When I go to add this app, that question does not come up, and any modification to it is lost when I exit.