New category duplicates post from existing category

Hi,

I’m trying to create a new Sidebar_right section or ‘category’on my site. I’m using a pretty basic theme (Flexibility Theme). When I create the category using the ‘category’ widget, it populates with all of the entries currently listed under a different category. How can I add a category and not have it duplicate the items already showing in another existing category?

Thank you!

Barry