adding songs for outright itunes newbie

Windows 10. iTunes version 15.2.x.x

I am searching for some place where effect of the button is to:

Click here then select a directory and add all the songs found in that directory and subdirectories.

I added iTunes to my Windows system and already have an extensive list. How do I add them all to the play list?

None of the four categories displayed below match so I picked one.

Thanks for your time