Well first off if find a post that you want to comment on click on the title. Then look in either at the top or the bottom left hand corner.  Once you have done this look for something like 0 comments or something of the sort.  Or if you scroll down and it has a little text bubble for you to right in.  Click on the inside of that box.  Then you would be ready right down your comment.  If you are done with your comment just go down it should have your name and website filled in.  If has something that says something like this grapes juicy.  Go above that and type what is in that box (it is usually a bright color so that you notice it).  Then just hit post comment.  If that works you successfully made a comment.