Go to ZeroTier here[zerotier.com], and click on login at the top right.
Click Create An Account

Here you will enter an email, and choose a password

That's it, account creation complete. You are automatically set up with the free tier. No email verification needed. Now let's move on to setting up your new network.

Assuming you have finished creating your free account, you should now be looking at your account page. Click on Networks at the top of the page.

Now click on Create a Network.

This will auto create a network for you. At this stage it will have a random generic name. You can change that later. The link to navigate to the network you just created is blue and consists of random letters, and numbers, with the generic network name next to it. Now let's go check out your network.

Here you will see your network ID in a few places. Also your Network name. Here is where you can re-name the network to whatever you'd like.

Now let's click on download to install ZeroTier.

Click on MSI Installer (x86/x64) under Microsoft Windows ( if not on windows, then choose the appropriate link )

Go through the install wizard, run ZeroTier when install completes. Enter your email, and password you chose. Now that you are running ZeroTier, and logged in, let's move on to adding your friends to your network, and allowing them to join you on Feel The Snow.

Go to your taskbar, and right click the ZeroTier app icon. Here you will find your Node ID at the top( also known as your Member ID ).

You will have your friend/s give you their Node ID, and you will go to your network via the zerotier website. Scroll down until you see the section MEMBERS. Paste your friends Node ID where it says "Manually Add Member", and hit enter.

Now they are authorized to join your network.
Your friend will now right click on the zerotier app icon on the taskbar, and click join network.

You remember where your network ID is located. On your zerotier network page via the website, or on the zerotier app menu by right clicking the app icon.

Copy your network ID, and paste it to your friend. This is what they will use to join your network.

Now you should see your friend on the network under the Member section on your zerotier network page. Your Node ID (member ID) is always first on the list, but underneath your ID, you should now see their Node ID (member ID). Now you are all set to do some co-op Feel The Snow. Open the game. Host your server (friends only - no password). Once you are fully loaded into the game, your friend can then open the game, and click Play > multiplayer > join server > join via LAN, and here is where they paste the IP of your virtual network. Your virtual network IP is next to your Node ID in the member section on your network page.

Enjoy Your Game !