How to have catergory drop down list in page menu bar (the main menu)

Hi there

I currently run a parenting website www.mumsbabymagazine.com and had a really nice theme which I designed in artisteer and then somehow AGES ago managed to add a drop down menu for the catergories (which I then called Articles) so that users could select a catergory and if they wished a subcatergory to browse articles upon relevant areas.

However, I have since changed my theme slightly and uploaded it and somehow have LOST the previous version and cannot find any code which I previously used... I am not a techy kind of person but I do remember the code was fairly simple and easy to install somewhere in the maze which is Wordpress...

Can anyone help me add my catergories (which will be called articles) into the page menu bar (the main menu bar). If you go to my website you can see the main menu which has
Home, Advertising, Contact Us, Links, MBM Forums

I would actually like it to be

Home Articles Advertising MBM Forums Links Contact Us


Can anyone help me somehow add a drop down for the articles (catergories).... Please please please please?


Rachel