If you check under MyVSL, you'll see there is another program you can download called Vienna Ensemble.
Download and install this. This program is like a mixer and it hosts all the Vienna VST products in one window so you dont have a bajillion windows open for each instrument. As a side note, the pro version of Ensemble will add the functionality of hosting other products that are not Vienna.
When you install Ensemble, in your DAW, add an instrument track, and choose Vienna Ensemble. Finally, in your DAW, add some midi tracks.
In Ensemble, right click on any of the open space and a menu will appear. In that menu, find and select Add Synchron player. This will create a single midi track with Synchron. This is by the way what Paul meant, you cannot run Synchron outside of Ensemble, it must be run inside Ensemble.
To add additional midi tracks, you'll right click and add another instance of Synchron player. Along the left side of Ensemble, you'll see the list of all your Synchron instruments and the midi channels they are assigned to, just click the title bar of each one to switch to that instance of Synchron and load / make changes to that instance (loading a new / different instrument, articulations, etc).
It is very confusing, I ran into this problem when I first started, among many other problems that are related to my not knowing anything about midi.
I do believe there is a video overview of Ensemble, if I were you, Id give that a quick watch, most of it is pretty intuitive, but in case it isnt...
Hope this helps, and I hope Paul doesnt mind my jumping in here, I dont like seeing people upset. This is an amazing library, and while the install process is a bit wonky, its pretty damn good compared to some other libraries Ive used.