There are a couple of ways you can interact with the different areas of the community.
Did you read a question and you think you have the answer? Click on the Add A Comment button to start provide your answer.
Is there a discussion or document that you think might have an error or something incorrect? You can click the Not Helpful button and then add a comment in the discussion.
Did someone post something vulgar or spam-like in a discussion, document or any kind of content? You can click on the "Actions" link in the top right side of the window and then choose "Report Abuse" in order to flag something for the moderators to come take a look at.
Most importantly, the more you post and interact on the site, the stronger the community will become.