Menu intrepidity theme

I have an small question. I use WP 3.0 with the intrepidity theme. where can I add an menu item. I tried this through the backend and this didn’t work.

I also looked at the header.php but did not thee the code for the menu. Any one an idea where to look where to add an link to the menu? I searched the Net for a few days and cant find it. I think that i’m overlooking something?

I use the theme on my blog on http://superdaantje.nl

Many thanks for your help in advance.