How to implement geofencing ?

You may want to start with this article: Monitoring the User's Proximity to Geographic Regions https://developer.apple.com/documentation/corelocation/monitoring_the_user_s_proximity_to_geographic_regions

Thank you. Example application triggers the message even when the app is not used but in my real application, it does not trigger the notification message. I have followed all the steps.

In my application the initial viewcontroller is Tabbarcontroller and the geofencing code is in third tab if that matters? Any idea why it does not send any notifications?

Be sure to test the results for your needs, keeping in mind that there is a built in delay before notifications are sent - the purpose is to confirm the user/device isn't just casually moving in/out vs. committing to one state or the other.