Api usage help - creating and linking geofences

Hello, could anyone exemplify how to use api to create a geofence associated with groups, users and devices?
In this way would there be duplication of pre existing geofences?

I'm not sure why there is some confusion. When you create a geofence it's linked to your user. You can then link it to devices and groups. Admin can also link it to other users. Linking geofence doesn't create any duplicates. That's why it's called "linking".

reformulating the question:

1. I would like an example to create through the api a circular geofence of x meters in a certain coordinate and associate it with a group.
2. the same request executed twice would not duplicate the fence? how could it be avoided?

1. Look at the official app for example.
2. If you send a create request twice it will obviously create two geofences.