Mark, welcome to the site. There are several ways to post a thread. If you are reading one of the threads from the home page and decide you want to add to it, you can use the Post Reply button found at the top or bottom left of the thread, or you can use any of the buttons in the lower right corner of each post. The Quote button means you will include the contents of the post in your reply; the + button is for tagging multiple posts to quote in your answer; and the last icon with the feather only is a Quick Reply which opens the window at the bottom of the last displayed post. Others have suggested you create a new thread in the Who We Are Forum (click Forums at top menu and click on the Who We Are Forum name). You will see a New Thread button at the top left of the list of recent threads - click it, give your thread a title and have at it!
Hope this helps....