To post a New topic:
On the main index page click on a forum:

At the top left hand side, look for a button named "New Topic"

Click this button and you will be taken to a posting screen. Fill out the titles of your topic then type your message. You can add smilies and bbcode if you desire. At the bottom of the message body there will be a "Sbmit" button. Click this once and that 's it.

Posting a reply:
On the main index page click on a forum:

At the top left hand side, you will see two buttons "New Topic" and "Post Reply" Click the "Post Reply" and you will be taken to a posting screen.

Type your message and click submit.

Also at the bottom left of the last post, there will be the same buttons plus a third one for "Quick Reply" This button will open up a drop-down reply box. This is so you don't have to wait for a new page to load.

Hope you find this tutorial helpful