There are a couple of ways to achieve your request.
- One could be simply configuring a port - forwarding rule in the router's firewall. However, this method leaves your camera accessible from the WAN by anyone, thus making your camera's network not secure. Please review the example provided in this link for a more detailed configuration explanation.
- Also port forwarding could be configured in combination with a VPN improving overall security and limiting accessibility of a camera. Refer to this wiki page for a configuration example.
- You can also use RMS VPN Hub service to access the camera, however keep in mind that the RMS platform is designed for remone access, management and administration purposes. Using the platform for video streaming will result in high data consumption and might not be a practical solution since the subscription to RMS VPN is based on data consumption. Here is the link to the video on how to configure access to the camera with RMS VPN.
Another thing to note is that if your camera does not have a static public IP, you will need to use Dynamic DNS service to maintain access to the device when the ISP changes the public IP. More details about DDNS capabilities and configuration on RUT360 are provided here.
The end solution depends on your use case requirements.