How to seperate external IP addresses?

Hi again, friends at TechRepublic! I am setting up a simple SSH server for remote access. The server is just an old computer that I set up that runs off my network. (It’s not a big server, because I don’t need it) So, the problem is, I go to a website like “InternetFrog” to see what my external IP is. It says my IP, lets say… “11.222.33.44” (obviously not the real address), but when I saw my external IP on another computer in the same network, it was still “11.222.33.44”. Also, when I tried to connect to the server with PuTTy, it says “Failed” I assume it’s because it doesn’t know which networked computer to connect to, because all 5 of them share the same external IP address.

Is there something I can do to fix this?

Thanks!