Welcome to the growing ISC family, first few days you can scan through the forum and article sections.In the forum, you can read the thread, view the answers already posted and express your opinion in the form of a short paragraph or two. Generally, we do not reply to forum threads or posts that are more than 10 days old.
You can read the articles and respond to it by adding further details relevant to it. Once you go through the articles, if you find that you can also contribute an article on similar lines, then please read the article help topic and start off.
You can also check the ask the experts section, if you find any questions that are in your field of interest or profession, then you can reply but be cautious as irrelevant replies will be stuck off. All the very best.