Instructions for Debian 9

Right-click on the desktop and select "Open Terminal" from the context menu.
In the window type su, enter the root password, then run the command:
apt-get install openvpn network-manager-openvpn-gnome

Wait until the installation is complete:

Now go to the billing panel and download the configuration file, or create such a file and copy the content from the text field in the billing.

Create a new vpnconfig directory in your home directory and transfer the downloaded configuration file there. You can do this with any file manager.

Then click on the Network Manager icon and select “VPN Connections - Add a VPN connection" from the menu.
In the window select "Import a saved VPN configuration" and click "Create":

Select your configuration file and click "Open”. Click "Save" button in connection properties window:

Connection completed. Click on the icon "Network Manager" and select your VPN:

Connection OK:

Now use some service to determine your IP address. For example, here. It must differ before and after connection.

Our congratulations, everything is ok and operates properly.