Can see vst's in Plug-In Information but can't access

I’m using Cubase AI6 in Windows 8. It was bundled with my Yamaha S90XS synthesiser.
If I go into Devices:Plug-In Information then I can see many VST’s installed (eg Flanger, Grungalizer), but I can’t seem to find these anywhere in the Project window where I can use them. I’ve tried inserting new Instrument, Midi tracks etc, but the only options are the S90XS or Halion.
How can I use the VST’s?
Many thanks in advance