Well how are you trying to use the VSTs? Are you trying to record something in and then use the VSTs as effects on that signal? Or are you simply trying to add effects to a recorded audio signal inside of Reaper?
As far as getting your audio interface I would make sure you have all the drivers installed. Are you using a PC or Mac? I don't use a Fast Track or Reaper but it shouldn't be too difficult to figure out. Have you set the signal to go out of the interface in Reaper? You essentially need to set it up so that anything going into
your computer first passes through the Fast Track and then anything going out of your computer (speakers or monitors most likely) is coming out of the outputs of the Fast Track. Check under preferences of Reaper, it will probably have a section where you can set your audio interface to work with it. If you don't have the drivers installed this may be an issue so make sure you are up to date with Fast Track drivers which are most likely available online if you search.
Then, once you have sound, if you want to effect that signal with VSTs it would work something like this. Say you want to record a guitar for example.
Either plug the guitar into a line input on your Fast Track or mic up an amp, whichever you prefer and have the I/Os for on your interface. Then once you have the signal going into the computer you will need to set up an audio track inside of Reaper that is armed to record. Put the VST on this channel. Then to make sure you can hear what you are doing, you will need to do what I stated above about setting your Reaper to
work with your audio interface. Basically set it so your main audio output is the Fast Track. Then on your outputs of your fast track you will plug in your monitors or speakers. You should now hear the guitar being effected by the VST come out of your speakers as you play. You can also record the signal in dry and then throw the VST on afterwards if you prefer a bit more flexibility in that regard.
Does that make sense to you? Is that really what you are even asking? If you can expand on what you are trying to do with your interface I could get a bit more specific for you. You may have to dig around for drivers and you will have to figure out how to route the interface into Reaper but those should both be very easy to do. If you need help let me know.
tried this still not working,.. not sure what im doing wrong