Just get you and whoever you want to play with to both install Hamachi (it's a free download program). One of you will create a room in Hamachi and assign it a password, the other person will choose to join that room and enter the password to gain access. You all now have a Hamachi VPN established. Now all you need to do is make note of the game hosts Hamachi IP Address (which will be displayed next to their name in the Hamachi window), and everyone connects to that address.
I'm not sure if there is an easier way to explain this as it's very simple, just make sure everyone has matching versions of Hamachi. Lastly, I know later versions of Hamachi had issues with creating LAN games with "some" games, which is why our group uses an older more stable version. I'm not sure if Civ4/FFH is one of those problematic games, but I'm pretty sure it isn't, so everyone just downloading the most recent version of Hamachi should be fine.