I have drums programmed in Guitar Pro...exported as midi...

No. You can't add more samples in SD2.0, for that use Battery or another sample loader. What you can do is use a triggering plug-in such as ApTrigga or Drumagog to trigger some samples using the hits.

And if you use your midi straight from Guitar Pro, you should at least change the velocity of the hits to make it sounds real (because that's what you use SD2.0 for).