[SOLVED] Unable to Add Categories to Menus

I posted on the wordpress forum but haven't been able to fix the problem.

Here is a picture of the page I'm working with:



I have created a number of menus and have posted a number of articles into certain categories, however none of the categories show up on that page. I can create a new menu but I can't actually put any categories on it. Why is that?

I can go to the category and see all the articles posted there, so the categories definitely exist. Why don't they show up on this page so I can add them?

Thanks