Hello Christian,
As far as I know, it is not required to use the WSF file to accomplish the task.
All you need is to create an instance of the "VixCOM.VixLib" COM object in your script, and you will have access to its methods and properties.
The WSF file contains constants you may need to work with the object, so, you will have to get the values of the constants from the WSF file by creating a simple script outside of TestComplete - the script will get the values of the constants and show them in a message box. Then, you can use the values of the constants in your TestComplete script.