One way to create a new category is to make an entry in the register. I would go a register. Turn off ShowTransactionForms. Then click to the non-single line mode with Ctrl+T.
Then enter a category and maybe a subcategory into a transaction. Don't worry about the category groups which Money will ask about. Those are not important to you.
Another way to make a new category is click Banking->AccountTools->Categories&Payees->Categories to get
you to Categories. Even better, you can click Shortcuts at the top, and configure in Categories (and other favorite places) for
single-click access.
Then click New at the bottom. Money will ask if you want a new category, or if you want a subcategory for an existing category.