There are 2 ways to arm and disarm your security system.
With the app
To arm the system, go to the Prevention section or the Alert control panel and tap the Away icon if you're leaving home or the Stay icon if you're staying home. To disarm, tap Disarmed.
Or
With the keypad
To arm the system, press the Empty house button if you're leaving home or the Full house button if you're staying home. To disarm, enter your 4-digit access code and press the off button.