Editing macOS Application "About" Panel

In an application such as the native email client on macOS, there is an “about” menu item under the “Mail” menu up in the top bar. How do I add items to the window that pops up that gives copyright info on the application? I know how to edit the copyright line and version, but how do I add an text that gives information about this project to this pop up?

I can’t find much online for this and I have tried messing with the Custom macOS Application Target Properties quite a bit and I still can’t find how to get it to do what I want.

Here is the panel that I am talking about that I want to add text to:

Apple does not make finding this sort of basic information easy, in this case start with the documentation for NSApplication, which is the default main class for a Mac Cocoa app. Under the section "Managing Windows, Panels, and Menus" you'll see one of the entries mentions the "About panel", follow the link...

As you descend into the rabbit hole you will find functions for displaying the About box and details of options which effect its display, go all the way down to the detailed description of the individual option keys and there you will discover the details of how Cocoa finds the bits to make up the About box.

HTH