How to create an in-app tour using tutorial_coach_mark?

I would like to integrate tutorial_coach_mark to create an in-app tour.

https://pub.dev/packages/tutorial_coach_mark

Unsure how to pass the key for a widget to use in GlobalKey.

Any ideas on how to integrate the https://pub.dev/packages/tutorial_coach_mark package please?

Thanks so much in advance for your kind help.