If you've found the answer you're looking for, you can close your question by choosing an answer as a "Best Answer".
To do this, while in Answers select the "My Stuff" tab and click on "My Questions" in the drop-down menu. Under "My Open Questions", click on the question you would like to close. Under everyone's answers, you'll see a link that says "Select As Best Answer". Click that link under the answer you would like to choose as the Best Answer.