Hey @gsb216200. Is the ADT system include a Ring Video Doorbell? If it is a product that we have made, you can set it up in the Ring app as long as it not hooked to a previous owner. Once set up in the Ring app, you can pay for a Plus or Basic Plan to cover your video storage.
For the security system, is it a wired or wireless system? If it is wired, you can use something like our Ring Retrofit to utilize the wired contact sensors from ADT. In the event that it is wireless, you will be unable to connect them to the Ring Alarm Base Station to be professionally monitored, as only a Ring Retrofit Kit or Ring Alarm Devices can be professionally monitored. You will need to buy a new kit here to get started with the Ring Alarm system in the event that it is wireless.