The question has since been closed as a duplicate. If you run across a question that you've seen elsewhere on the site, you can use the
flag option to bring it to the communities attention and others can decide if it is indeed a duplicate question or if it stands on it's own. Once flagged as duplicate, a comment will be automatically generated alerting OP of the possible duplication and it's up to them to either remove their question, allow the community to close their question, or edit their question to make it distinct than the linked possible duplicate.
Marking an answer as duplicate is as follows. Clicking the
flag link underneath the question then clicking the
duplicate of radio button. This will allow you to paste the URL of the duplicate question.
While you get no points for pointing out the duplicate, it may help the original question asker find their solution faster and overall helps keep the community cleaner.