Download Beamtic's connecter for NordVPN (Source included), and follow the instructions in this tutorial.
Edit January 2019: NordVPN now have their own Linux client, with more options for connecting, so it is no longer recommended to use Beamtic's Connecter.
Using NordVPN in Linux is actually not very hard at all. It does lack the convenient GUI we know from Windows, but connecting from the terminal is fairly straight forward.
We created a console app, which may make it even easier to use NordVPN in Linux. The app works by showing you a list of VPN servers, you can then connect to a server by typing the number of the server, and hitting enter. The app then opens a terminal window, and automatically enters the command to connect.
1: Start by installing the OpenVPN client from a terminal, as you will need it regardless of which method you use from this tutorial. You may install OpenVPN by entering the following command in a terminal:
sudo apt-get install openvpn
2: Then Download NordVPN server configuration files, and unzip them in: /etc/openvpn – do this from a terminal:
cd /etc/openvpn` sudo wget https://nordvpn.com/api/files/zip
Connect using Beamtics console app
3: Then download Beamtic's console app from here (c++ source is included)
4: Unzip the files from NordVPN-Connecter.7z to the directory: "/opt/NordVPN Connecter"
5: Drag and drop the .desktop file from "/opt/NordVPN Connecter/NordVPN Connecter.desktop" onto unity for convenient access. Left-click to connect, right-click and choose disconnect to disconnect.
You should be able to close the terminal window after connecting, but you can leave it open to easily disconnect later by pressing Ctrl + C.
Connect using terminal commands
3: To get a list of servers that you can connect to, enter the following:
cd /etc/openvpn ls -al
4: Then connect to one of the servers:
sudo openvpn [file name]