Here's a short guide to help you get started hosting a server, which might not be as specific as you need but will at least help you know what to google if need be...
- Most guides recommend you have a Static IP address (meaning your IP doesn't change if you disconnect-reconnect). I don't know if that's a requirement but it's a good thing to have in any case.
- You will need to access your Internet router's (modem) settings. You do this by putting your router's IP address in your browser (http://192.168.1.1/ is common) and logging in (will likely be using a factory default login). If you're not sure of any of these things you should be able to google the make of your modem to find them.
- Find the section in your router's settings called something like "Port Forwarding" (it might even be in a videogame specific section).
- Add a port forwarding entry for your public Restricted-RPS server by inputting the port you're using for the server, setting the protocol to TCP and setting the external port to one which allows the internet to access (2? it should say somewhere on the router page in any case).