How to use app2png?

I want icons images of applications.
Wen i right click on icons >adds on>file type>click 2 times
the it displays an empty window of Ion-O-Matic

In Terminal, you have to be in a writable location. AbiWord sits in /system/apps/ and isn’t.
So, open Terminal on your Desktop, for example, and enter app2png /system/apps/AbiWord.

Opening via double-clicking in the FileType add-on only opens Haiku’s vector icons. Yours are all old BeOS apps.