Help making fullscreen?

So when I hit p to play only some of the screen is actually played How do I make it full screen?

I’m new to blender myself but I guess that would be in the camera settings, can’t tell you where exactly.

I do not think that you can get fullscreen when running the BGE inside Blender.
You can get it with the runtime version of you game.

Since Blender 2.5 the area outside the active camera is not rendered by the BGE.

you could change the res to some wide screen resolution or change the camera focal lens.