resizing the main camera window in Unity 5

Hi,

Im trying to resize my main camera window to a smaller size. But when I try to resize my window
it resizes the entire window and thats not what I want todo. I want to be able to control the width and
the height. Ill just show you the example of what im trying to create

 

Try changing stuff in the inspector &/or moving the camera closer

 

In the Game tab, click on the menu in the top left corner, and pick the size you want (or define a new one).