Mike,
The popup window is a webscreen like the others. You can just change the layout to whatever you want.
Edit the screen the same way.

How do I choose which screen to show for the popup?  I don't see an option for that in the properties panel:

You have to select a link or button, of which you need to give a name so you can see it to select it.

And it's on that link or button that you choose where to go, by choosing onclick method to navigate and as destination the webscreen.

Got it, thanks Tiago!

I forgot... The On Notify on your image is the action you want to run once you close your popup. When you close it, the On Notify will take care of the request.

And to trigger that On Notify you must use the Popup_Editor_Notify action.

Michael, I don't think you understood the dynamics of how that pop-up component works.

1. You implement some screen, with the layout and functionality you wish
2. On another screen you already have, you add a link to this new screen
3. Next to that link, you add the pop-up widget. That widget will open your new screen inside a pop-up, instead of redirecting the user.

So you don't specify the screen on the pop-up widget properties. What defines what the pop-up will show is the link you've created.

Thanks for your assistance everyone!  I got it working--the way I thought it worked was slightly different than how it is implemented.