There's 2 ways I can think of doing them:
1) Create popup in editor on a layer and turn visibility on/off
Pro: easy to set up in the editor
Con: items in the popup will still get updated even if they are not visible and take up memory (performance)
2) Spawn & destroy popup as needed using system -> create object
Pro/Con: basically the opposite of layers... annoying to create because the popups consist of lots of pieces so lots of 'create object' actions are needed but probably better performance wise
So far I've been using the layer method, but now that I'm up to 6 fairly graphical popup layers that are invisible most of the time and want to add another 2 I'm starting to wonder if there's a better way.