The posting process is basically the same whether you're starting a new thread or replying to an existing message.
When you're on the screen for composing your message, you'll have some options...
Subject: If you are replying to a message, this will default to "Re: [title of the message]". You can change this if you want. If you are starting a new thread, this will be blank and you should enter a subject/title for your message here.
Body text: This is where you compose the body of your message. When you've completed the message, you'll have the option to preview it or post it immediately, depending on which button you choose at the bottom of the bottom of the form.
If you're using markup, previewing will allow you to make sure you did it right. Even if you're very familiar with the markup codes, you could have always made a typographical error and it's better to catch it now before you send the message out into the world.
IMPORTANT NOTICE: All posts are governed by our terms and conditions of use. When you post a message you are agreeing to them, so you should read them carefully.