From the terminal on Ubuntu 17.04:

sudo apt-get install network-manager-openconnect network-manager-openconnect-gnome
sudo systemctl restart network-manager
sudo systemctl daemon-reload

Under Network Connections (nm-connections-editor), click Add > Juniper Network Connect (openconnect), and set up with appropriate details for the desired VPN connection.

Juniper Network Connect (openconnect)

Now when you attempt to connect to the VPN, you’ll be prompted for your credentials.

Adapted from