Thank you for your reply and sorry for the delay of my answer.
Obviously I was not clear in formulating my question. I am able to create Topics from the Administration (Content Management > Topics), but my problem is how to make the particular topic to appear in the particular Forum.
Lets presume that I have a Forum called Test and a Topic called TestForumTopic. I do not know how to make the Topic to appear under the forum called Test. Where (which page, control or...) do I need to add the Topic URL in order to achieve this?
I hope that now my question is clearer. Actually I am having problems not with creating the Topic for the Forum, but with providing this Topic to appear under a particular or the only one Forum you have on your web site.
I am sure you will be able to advice me how to do this.