Normally rotating the screen to portrait mode is a function of your screen driver or operating system rather than of software such as Finale.

I have rotated the screen to portrait mode in Windows, but I am not sure how one might do it on a Mac.

Mac OS supports monitors that operate in portrait mode. Not enough info to comment further.

In your system preferences, under display, you'll see the option to rotate your view from standard to 90 degrees. That's just a function of the OS. Now some monitors have the ability to rotate on their own. Others require a monitor clamp which will attach to a desk and can rotate your monitor in any direction.