Turn the big knob to scroll through the characters. Press the 6 key to advance and the 4 key to go backwards. Press the big knob after you entered the password.
Passwords are case sensitive so enter exactly as you have on any other WiFi devices you are using at home.
You will have to use DHCP in your router so it will assign an IP adress to the scanner when it logs on.
Or if you can lock the scanners MAC adress to an IP number in the router you will have to do that if you do not use DHCP.
Go to the scanners menu system and scroll down to WiFi Setup. Go to Show WiFi Information. If you have an IP number there you are connected to the network. In the Siren app you set the exact same IP number and it should connect, if the mobile phone are connected to the same WiFi network.