I am linking a guide to getting started with an existing system below, but in general if you have an existing system which is compatible and the IMEI is not currently registered to any ADC account, you can get started by purchasing your chosen plan on our store here, then you will be prompted to activate service.
Activation is a few step process on our website which includes completing an activation form that collects the necessary details for your account. It can take as little as 5-10 minutes to start usinng your system if you are near the system and ready to go.
If you have compatible Alarm.com video cameras consider the Protect or Complete plan. Complete also includes automation device support like thermostats, lights, door locks, etc.