You'll need a VPN to be set up. The VPN will make it seem like your device is on the LAN even when you're away from it.
One other option that is not recommended, is to port forward your cameras to the public internet. This will allow anyone to access them from anywhere.
Are you using a NVR or PC for recording? Some of us just connect to the NVR/PC via VPN, port forwarding, or TeamViewer.