How to answer to my question on this forum?

Hello,,

I am trying to reply to a query in one of my questions

http://ask.ocsinventory-ng.org/9999/installation-issue-in-plugins

However I don't see an Answer button at all. 

How do I do it? Screenshot pasted below. As you can notice, there's no answer button.

Image may be NSFW.
Clik here to view.

Thanks,