The simplest way of reaching a server hosted on your home network from outside of your network is to port forward traffic on a specific port to a specific ip. Say for instance all traffic on port 8096 to the ip of your Jellyfin server.

Google the brand name of your router and port forwarding to find out how.

But that is not the most secure solution and should preferably only be done if you understand at least the basics of network security.

The better solution would be to have an encrypted VPN service to the inside of your network. This solution is a bit harder to set up (though not as hard as you may think). This would allow you to view any hosted services as if on your home network from anywhere in the world.

I would recomend studying the VPN option. OpenVPN is a free option that can be hosted on a raspberry pi, LX container or most any other server option.

Edit: If you port forward on your router the correct way to reach the Jellyfin service outside of your local network would be to enter your public ip followed by port. Your public ip can be found by googling “whats my ip”. The result should look something like this 92.16.23.54:8096