After the success message, switch to the settings via the quick settings menu.
Settings via menu
Navigate to "Network" and click on the "plus icon" above VPN.
VPN plus symbol
Select "Multiprotocol VPN Client (Openconnect)".
Choose VPN connection type
Enter vpn2.zih.tu-dresden.de as gateway and open the CA certificate (download to the right of this instruction). Then confirm the information with "Add".
...with the new root certificate "SectigoChain.pem"
Enter gateway and CA Certificate
After you have activated the VPN, you have to enter your username and password. Make sure that you use this form for your username: zihlogin@tu-dresden.de.
Afterwards you can click on "Connect" and you are connected.
Enter your credentials