Before adding cameras, ensure you have set the storage location in the Settings menu and created an onvif user with admin rights for your camera.
Login to the VXG Gateway/NVR.
Click on Add Camera.
Click on IP Camera and click Next.
Fill the fields specifying the URL field (onvif/rtsp) as seen in the picture below replacing the ip address with the address for your camera.
...
Enter username and password for your camera.
Toggle the recording for the camera (optional).
Click Next.
Setup complete.