When you click on a forum on the main page, you will be taken to a new page with a button near the top-left. Click on this button to enter the 'Post a new topic' page.

The first thing you should do is add a subject title. This describes what you are talking about in your new topic and allows users to instantly recognise the purpose of your post. To enter a subject title, type in the bar next to 'Subject' on the left of the screen (above 'Message body' and emoticons).

Next you will want to make sure that you are using your preferred editor mode. There are two editor modes to select from: Standard and WYSIWYG (What You See Is What You Get). For those unfamiliar with HTML or BBCode, it is recommended that you press on the button until it turns pink in colour (as pictured). You will notice that in WYSIWYG mode, everything you type appears as it would once it is posted. In other words, what you enter in your post now is exactly how it will look once you click on the button.

For example, clicking on (Bold) button and then typing a word such as 'Green' will return this result:
Green

In the standard editor mode, doing the same as above would instead return this result:

Once you are happy with your post, simply click on the button and you will be taken to the thread you have just created. For further information relating to 'Posting A New Topic', please reply to this post with your question.