It looks like you've created a free space page for Victoria (not a category), and put it in the Australia category.
Because Victoria is a state, according to our naming conventions the category should just be called Victoria, not Victoria, Australia. So to create the category, you need to go to http://www.wikitree.com/wiki/Category:Victoria
and edit the page. Since it should be a subcategory of Australia, you just need to put [[Category:Australia]] on that category page.
Let me know if you have any more questions about this!