To play Making History online is simple and easy, I'll list a few steps you can take to play with anyone you like.

1. Download Hamachi and Install hamachi.
2. When installed, click the power button. (It'll make you get online in hamachi)
3. Click on the network tab, and click "Create new network" (If you're hosting)
4. Name the network whatever you want, and create it.
5. Tell your friend the network name and password. Your friend (The person who is not hosting) will click on the Network tab, and click "Join existing network" and enter in the given info.
6. When he's in your group make sure that both of your connections are green (Indicated by a colored dot next to the username), if not, it may not work.
7. Launch Making History
8. Click Multiplayer
9. Click "Host new", and select the scenario you want to play in. And the country you want to play as.
10. Your friend will now also go to multiplayer, and click Join, after a little while the server should pop up in the "Server games" list.

-----------------If The Game is NOT showing up in the list-------------------
If it doesn't, bring up your hamachi window, right click on your IP next to the power button icon, and click "Copy IPv4 address", give it to your friend and tell him to click "Add server", type in the address there, and click either IP or Network. Try both if its not working.