With Debian 7 or Mint 17 that come with the MATE desktop, it appears that Network Manager does not manage connections by default, so a few extra steps would be needed compared to an install using Gnome or KDE Desktop Environments.
Step 1: Open Terminal
Step 2: Install OpenVPN, and Network Manager
sudo apt-get install openvpn network-manager-openvpn-gnome
This will put the Network Manager icon in the task bar, but network Manager is still not managing your network connections at this time
Step 3: To remedy this, type the following in terminal:
sudo nano /etc/NetworkManager/NetworkManager.conf
(You can use any editor that is installed; like nano, pico, or vim as a few examples) This is in a critical system area on your Operating System, so you need to Sudo, and confirm your computer Admin password to be able to edit the file.
In your text editor, you are looking for the following:
You want to change it so it says:
Step 4: Now we need to restart Network Manager to make the new setting take effect. Type the following in Terminal:
sudo service network-manager restart
After these steps are done, you can simply follow the setup instructions here.
If this doesn't work on the first try, reboot, and test again.