Assigning survey questions to categories

I have a survey for a class. There are 20 questions and 4 categories (5 questions for each category). I would like to display scores for each of the 4 categories.
The categories article has a screenshot displaying piped text for each category. I assumed this can be at the end of the survey (or next page). I know it can be accomplished with total score. All of the categories on the article page are displayed as having "0 items." How can qualtrics calculate a piped score for a category when it has 0 items?
However, it doesn't say anything about how to assign a survey question to a category. Is this possible? If so, how is it done? Thank you.