Where do I need to go to take the Korean proficiency exam?

This question is really in response to "Shinchon"s answer on a question of pronunciation on a different question. He had mentioned his score in Korean on that test and I can't figure out where I can take it.

I didn't attend langauge academy. My husband is Korean and we only speak Korean at home. I feel that it is pretty good (as I can understand most everything), writing and reading are also good, but I think that if there is a test I can take so I know what I need to improve on or how to get better resources, I'd appreciate it. Obviously my Korean friends don't no anything about the tes (because they've never had to take it:)

Help!