It only let me add Topics or pages but no subtopics.
To add a subtopic, you need to be in a topic first. You can’t do it from the overview. When you are in the topic, click +subtopic in the lower left corner. If it doesn’t have this, and only says +page, that means that your topic is a stack and not a planet-style topic. You cannot add subtopics to stack topics. You can get the results you want by starting the prezi from scratch instead of using a built-in template like this one. Take my online course, Master Prezi Next, to learn how.
Robin Pierman, www.teachmeprezi.com