"남자가 한국에 있습니다."
Translation:The man is in Korea.
I mentioned that here: https://www.duolingo.com/comment/24547746$comment_id=24675944
*한국 and yes -에 is the location particle. 있다 means roughly "to be" in the sense of "existing" so this sentence roughly translates to "the man is in Korea". I'd recommend taking a look at the tips & notes for the Basics 2 skill found on the mobile/desktop Duolingo website (not available from the app unfortunately)