Make sure the following components are installed.
In the example we use Ubuntu. There the necessary packages have to be installed as follows:
sudo apt update && sudo apt install resolvconf
The main window will now show the server list. With a click on the corresponding connector icon you can establish a VPN connection to a server of your choice.
When the globe symbol in the top right switches to green and Connected is displayed, the VPN tunnel was established successfully.
A click on the info icon will show the connection log.