Hi Rob,
don't despair. Firstly, A famous quote i read somewhere was "to do well, surround yourself by good people" and by being on this forum, you have done so. Secondly, the Kaplan test is not an accurate predictor of where how good you are and on this forum, the Kaplan material are referred to as "Kraplan". So to start studying properly, get some more reputed books/guides and start participating on the forums.
You will get more into it as a little time goes by. We all started somewhere sometime.
Most importantly, make GMAT fun and it won't be as daunting.