Viktor, if you mean "how to replace" your GPS antenna, it would be helpful if you could post a picture of the unit. They are probably available on the store at this web site or from Defender.com online.
If no picture is available, a brand name or detailed description of your current unit could be helpful in guiding you to a source.
If they look like the pics below, it's a matter of how it mounts on your boat and how it connects to your display.
Hope this helps.