The safest way do this is by actually contacting First Alert. The link below says it will help you configure your alarm system:
The reason for this, is because you don't just want anyone having access to your alarm system and access to your home.
What kind of alarm system is it? Is there a model #? This might help me find some information for you!
Below is their email address, in the event we are unalbe to assist you:
Well, I am glad you found the answer! If there is anything we can help you out with in the future, please don't hesitate to ask!