Ah, okay. First he uses the xrandr Command to show the available Resolutions in the List. And the Visual1 Name of the Display Device which is later important. And in your Case it could be named different. so, you have to look what it is named in Your Case.
Then he type cvt 1920 1080 because this is what he wants to have as the Resolution. And that gives him a Modeline Output what he needs. Then he create a new Resolution Mode with the Command xrandr --newmode [Modeline-Output]
After that he have to add the new Mode. That he do with the Command xrandr --addmode [Display-Device-Name, in his Case Virtual1] [Resolution-from-the-Modeline-Output] and then the Dispplay Settings will be reset and You have to go to Settings>Display anmd there choose Your created Resolution.
And after that he copies the newmode Command and addmode Command to a .profile File because the System seems to doesn't remember this Change.