There are various applications on the App Store that you can use on your phone to watch live streaming from your home or recordings. Typically, you should look at the manufacturer's website since many of them provide customers with all the apps they need to view the live streams from CCTV cameras.
However, to watch the streams, a port forwarding is necessary. Connect to the router administration interface and add the IPs and ports of the cameras so that you can access from outside your network.
Once you set up all the things, use an application like iCamViewer: https://itunes.apple.com/us/app/icamviewer-cctv-camera-ip/id346469891?mt=8