You can mark the "accepted" answer by clicking the check mark next to the answer you think is best. The check mark will only show up if you're logged in. The only person who can mark a questions as "answered" is the person who asked it.

Question would remain on the site for all to see and possibly use if they have a similar problem. As a questioner it would be pertinent to see if your question has been answered successfully and then use the vote feature to pick the best solution offered.