As an Admin, can I change the geofencing location which is assigned to the staff?

Yes, you can change the geofencing location of the respective staff as required from the Staff Directory.
Go to Web Dashboard -> Staff Directory -> Edit staff -> Access -> Geofencing Locations, you can select the required locations and save.

Alternatively, you can also do it via bulk edit Excel sheet by updating the data in the ‘Geofencing Location’ column and uploading it.

Or from the user app you can do it from: User App > Other Actions > Staff Directory > Edit Staff > Access > Geofencing > Select locations > Save