How to play Heroes of Might and Magic III online via Hamachi?

Hello everyone!
I have a question: how can I connect to a computer in another city over a network if both have internal IP addresses? I saw somewhere that there's a program called Hamachi, which allows you to either create your own connection or join an existing one. Here's the link: http://www.networkshamachi.com/default.asp?page=hamachi-games. I don't know if I need to download the program itself or just register on their website. Please advise, I don't understand any of this, but I want to play.

If the networks are linked, you can play without the internet (or you can see the server via TCP/IP, or connect by manually entering the internal IP address). If there is no link, you can only play over the internet, using Hamachi or similar. If using Hamachi, you need to set its priority in the network connections - to do this, open the network environment, display network connections, advanced, advanced settings, and move Hamachi to the top (otherwise, you will have to manually enter the Hamachi IP address each time). Hamachi is easy to install and use, and you don't need to register anywhere.