[Header] How to change header coding — please help… :-)

Hi!

I want to recode the menu on bil97.nl.

The problem is that my theme doesn’t allow me to make custom menus, so I can’t make one of my menu links redirect the visitors to external pages (ie http://www.guardian.co.uk).

I want to to that.

I can’t make those changes in the editor, because I can only edit the theme there.

So where in my ftp folder should I look?

please help me…