Android 4.4.4 Files Question

I have broken down and bought my first smartphone. A Motorla Droid Turbo running Android 4.4.4. How do you access the files on the phone? When I plug it into a computer I can see folders for ringtones and alert sounds and can add files without trouble but I cannot access the folders from the phone itself. Is there an app I need or is it buried somewhere in setup or elsewhere that I'm not finding?