Badges on app Icons and in app

I have an app with some notifications count, and I'd like to display this in app and on app icon on IOS/Android apps.

I can build something manually in the app fine, but I tried the Badge Widget which does not seem to work.

I have also tried (and failed) to install pub.dev custom badge widget "badges: ^3.1.2".

See images.

I am probably missing something in the instillation of the pub.dev thing - or maybe that's not the right approach.

Is there a recommendation/walkthru someone can help with?

Appreciated/thank you!