How to hide the bottom menu of Android?

Hi everyone!!

When I run the aplication, in the screen of the smartphone appears the navigation bar (return, home, settings buttons and black background). I modified the manifest.xml, use the sketch permissions, and other code with onCreate() functions, but nothing works. there any way to hide the navigation bar?

I read this: https://developer.android.com/training/system-ui/navigation.html But I don't understand how it works because it's my first time, programing with android. I'm using Android 5.1.1, and Processing 3.0 and the last version of android mode. Sorry for my bad English.

Thanks a lot!