How to get 2 Mac mini displays to have their own unique open apps, a set on A, and diff on B?

I've successfully got two monitors running on a 2012 Mac mini. But how do i get each screen to have it's own 'identity?' That is, how do i get 2-3 windows open on monitor A, and windows 4-6 open on monitor B?

They should be able somehow to have separate and distinct displays, right? Email responses greatly appreciated to:

jcrowconsult@gmail.com

Thank you in advance, fellow Mac mini users. ...