Its pretty simple, there is one bolt at each corner. The front ones need to be tightened, the rear ones loosened.
Here is a thread with pictures of what needs to be done:
http://forums.corvetteforum.com/zerothread?id=311973
I was able to turn the front bolts without removing the wheels, but it might have been faster to do so. For the rear I removed both wheels and turned them leaving 3 threads showing.
There are some other tricks if you want to go lower than this.
I can help you lower it if you'd like, it takes about an hour.
Eric