Hamachi isn't a server. It is a VPN (Virtual Private Network) service
wikipedia:
http://en.wikipedia.org/wiki/Virtual_private_network
Hamachi allows you to estabilish a network that works as a LAN, but over the internet. You can create a net in which you can invite your friends and then you can connect each other as if you were in a LAN network.
The actual minecraft server will be stored on one of the computer of the net.
To connect to the server you have to use the "direct connection" button in minecraft and manually put in the ip that
hamachi assign to the computer that runs the minecraft server (the xxx.xxx.xxx.xxx number that will appear next to the pc that you know hosts the server in the blue window of hamachi).
Hamachi offer limited connection speeds and a limited number of PCs per net (5) for free. If you need more than 5 slots or more speed you have to pay. Vanilla Minecraft goes great with 5 players and free hamachi. I never tried to make a FTB server.
I hope that it was clear!