If you want to host I think this is what you do.
I assume you are playing this with a freind
step by step:
If Hosting
1:Press power button on hamachi
2:you need to go to single player and select the diffuculty mode you want.
3:then go back to the menu and select multiplayer
4:then select host, next to port it should say 26000 if not change it to that.
5:select ok, then it should bring you to a menu of othions for the mutiplayer server.leave everthing the same and begin the mach.
6:open the console and type in which map you want to play, Exp:"map name the map"
If joining
1:you need to know your freinds ip for hamachi (yours will be displayed to you when you push the power button on hamachi.
2:then when at main menu in NZP open the console and type exp:"connect then your freinds ip.
This should work for you. true nighmare did a tutorial on how to do it on YOUTUBE.
https://www.youtube.com/watch?v=VbdMZgqSlxE