[HELP] Adding categories to navigation bar

Hi there I need some help with the navigation bar…

as you can see, there is only the ‘home’ link in the navigation bar.
I would like to add the categories of posts in there, like pictures and videos, I would also like to have a link in there to my forums (forums.themavesite.com)

The thing is ; I don’t have a clue howto do this :s
I searched a bit but couldn’t find anything that helped me ??

Please help me out