I just signed up today so I am learning the ropes right along with you. To answer a question, click on the question - scroll all the way to the bottom and on my PC, I have a text box that comes up that allows me to answer the question. Then I hit the ANSWER button and it saves my answer.
In regards to the comment question, I don't know that yet. However, I save Kass Yassin's answer from ASK.com in regards to how Blurtit.com works. Below is the response. Hope this helps.
Hey all, I actually run Blurtit.com and am always happy to answer any questions you have about the site. You can reach me on kass @ blurtit.
I had to break up the email address so would save it in the answer. Add dot com to the end and you'll come up with the email add.