Hmm I don't think there really is a good popup tutorial with details? Even the newest xpopup docs don't explain it...

Here's a brief explanation.

You'll notice that the popup.rc in your personal folder looks something like...

*Popup !New !Popup

Content

*Popup ~New

You must edit between those. The first line starts a new popup, and the last line ends the new popup. You'll also see lines like...

*Popup "some text" Folder

Content

*Popup ~Folder

...within the new popup entries. That creates a sub folder for more content.

Each *Popup "some text" Folder line must also have a corresponding *Popup ~Folder line to end that folder. Folders can be nested.

Content will generally be *Popup "some text" !bangcommand.

There are some popups !bangs that do not have to be within a new popup to be executed. Like if you want a popup to be shown with a folder's contents by clicking on a label, for example.

Have a look in the \litestep\modules\docs\(popup module used by theme) folder.