Button Click Signal to make a pop- up window

Hi, I saw a couple of topics about this but I didn’t exactly understand so I’m making this one to ask. I’m using Qt Quick and as suggested in the tutorial I made different .qml for every button. I want when the button is clicked to make a window pop- up. What should I write after  onClicked: in the mouseArea. Also how to make a second window (the pop- up one), what should I add to the project so I can design it like the main one. I read that I have to make a class that inherits with QWidget but I need a bit more information. A short example would be great.