how to reset factory fitted alarm on ford mondeo 1.8td 1995?

can anyone give me some advice to resetting factory fitted alarm on my car , every thing seems to work ok , the red light does seem to stay on longer when i turn ignition on but then goes out but i was told it will do that untill reset . this alarm does not have a key fob the alarm works just by locking i was also told . can anyone help?