Answers for "how to use window size"

get window size javascript

const window {
  width: window.innerWidth,
  height: window.innerHeight
}

how to change size of the window

To resize browser window 
-I would create object of dimensions class
Dimension newD = new Dimension(480,620)
-Than I resize the current window to the given dimension
driver.manage().window().setSize(newD)