This documentation was tested on fresh installs of Ubuntu Desktop 18.04.1 and 20.04.
Install the NetworkManager OpenVPN plugin if you don't have it. To do that, open Terminal and type:
sudo apt-get install network-manager-openvpn-gnome
Click on the Network icon in the status bar then “VPN” > “Connect” or “arethusa”.
Once connected, check your IP addresses.
The OpenVPN log is in /var/log/syslog , mixed with all other system logs. Skip until you see lines with openvpn.