The 'downloads' section of the manufacturer's website is currently completely empty. However, they'd probably email you the installation guide (in pdf format): [email protected]
The bell box will probably require a constant feed to 'hold off' from ringing. To completely and permanently power down you would need to disconnect the internal battery on the wall outside or just let it ring until flat.
Opening the bell box to disconnect the battery will set off the tamper circuit and you may then need the engineers code to reset the system when using the alarm again.