On your newly created Trivia app, go to the Questions section and click Create Question:
Edit the default text for the question and optional answers. You can mark any answer as correct or incorrect using the indicator to the left, and add more options with the small blue button. Always remember to save your work before leaving.
This is how the Questions section looks with an existing question. From here you can create new ones, edit or remove the existing questions. Whenever you edit a question to add or remove options, you must click Save Question before closing the window.