Well without actually seeing your site hard to say you even have things installed correctly.
Now based on the error your showing and the documentation I would think you do not have the proper information entered and it could be a number of things so lets break that down on some things to try.
1. First the easy one. You could by change not have the proper reviewpost database prefix entered under your edit integration settings in admin. That would explain the error your posting.
2. The second is a little more complex meaning the database information is not correct in the global variables plugin for the reviewpost product but first try the first thing.
You also want to post your url to your reviewpost install here so I can see if its installed correct.