Dear salammalas,
Information about setting up and changings of settings (including APN) the tracker is usually contained in the instructions (manual) for the tracker.
For most trackers, it can also be found online. For example, on our website in the section Devices https://gps-trace.com/en/devices you can find instructions for many trackers integrated into our system.
Also you can contact the seller or manufacturer of the tracker for questions about setting up the tracker, they will provide you with the most complete knowledge on these issues.
If you cannot find this information, please write to us type / model and manufacture of device , then we will try to check additionally and help you.