How do I have two windows open on the screen?

Hi,

Click on the smiling Mac face in the dock to open one window > hold down the control key and click on it again >

select New Finder Window.

Or

Click on the smiling Mac face in the dock to open one window or double click on a your HD icon on the desktop to open one > dc on a folder on the desktop.

Or

Hold down the control key > in the Sidebar, click on a folder or hard drive icon or the Desktop icon > select Open in New Window.

2 Windows of what?

Not all apps may support 2 windows, but if they can generally you can do so by control + click the application icon on the dock and selecting "New Window" or by selecting "New Window" from the File menu at the top.