If no VPN connection has been used before, please write a ticket to IT so that this can be set up!
Step 0:
The VPN connection only works outside the ZMT network. (eduroam, ICE, at home, etc.)
Step 1:
Right-click the FortiClient icon 
and select 'Connect to "ZMT VPN"'. 
Step 2:
The FortiClient should open with the 
selected.
At 1 & 2 enter your short username and ZMT password, check the box at 3 to save your password and connect using the button at 4.
Step 3:
Quick check to see if the VPN-Connection was established.
This can be done using the FortiClient icon 
(the icon has a little padlock now) or checking directly inside the FortiClient.
It is shown that the VPN is 'connected' and it is possible to 'disconnect' the connection.
Step 4:
After the username and password were entered and the 'Save Password'-checkbox was checked, it is possible to start and stop the VPN connection with a right-click on the FortiClient icon. To establish the VPN connection 
and to disconnect. 
The VPN connection can also be stopped directly in the FortiClient through the Remote Access tab and the Disconnect button.