When viewing the list of topics for a particular forum (such as DD's Help/Tips/Tricks), there is a 'New Topic' link on the left side, third line down from the top of the page (followed by a 'Forum Options' menu). It is just above the title row for the topic list (Subject / Poster, Replies, Views, Posted).

When viewing a topic, in the same place (third row down, just above the first post subject) you will find a 'New Reply' link (though the links to reply / quote at the end of each post are probably more convenient) followed by a 'Topic Options' menu.