Press the learn/connect button in or on the siren for about 8 seconds until it beeps. (all connections are deleted)
Get the W020 app in front of you and put it in disarmed mode (lock open).
Put any delay time to 0 seconds.
Press the learn/connect button in or on the siren once shortly. The siren will go into learning mode.
Press in the W020 app the arm button (lock closed)
The siren should be reacting to this action.
Now you can test if the siren is correctly connected by triggering an alarm with a sensor. Both the W020 and siren should sound. When disarming the system, either by app or remote, both the panel and siren should go off.