It would be by setting up a VPN server in your home which some routers support natively. You would then just add the system to the app using the NVRs local IP address. When you want to view the system remotely you'd start the VPN on your phone, which creates an encrypted tunnelled connection and you can access all devices in your home network as if you were there. However you won't get push notifications of events regardless of where you are, as Hik-Connect only supports push notifications when your phone and NVR are connected to the Hik-Connect server.