It is not that obvious how to do it. If you click on that little triangle it will allow you to report a post to the moderators. This triangle should be a ways below your avatar. Uses for the button. If you see a post or thread in the wrong section. If you see something that is not appropriate. If you see anything else that seems to be not right. Use some judgement when using the button but if you think it is something someone should look at by all means hit the button.