Arm the alarm without the key fab.
Open drivers door, have keys in hand or in your pocket, make sure all the other doors are closed properly, push the power lock button, make sure all the doors are locked and then close the door, if visible you should see the security light blinking.
OK thank you
If it's like my forester though, unlocking the car with the key, you will have to disarm the blaring alarm by turning the key ON-OFF 3 times.
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