When you post a question or problem, it’s good form to acknowledge when it’s answered or solved. Discourse makes this easy.
When you start a topic, you’ll see a button below every other post in the topic that will let you mark it as the “solution.” It looks like this:
Once you do that, the check box will also show up next to the topic title in the topic list, to let people know the question has been answered. A snippet of the post marked as the solution will also appear immediately below the first post in the topic.