To add a question to an existing page in a Microsoft Forms form, you need to follow these steps:

1. On the Home tab, select the page that you want to add the question to
2. On the Question tab, select the type of question you want to add
3. Use the Insert drop-down menu to customize the figures, charts, and other elements
4. Edit any instructions, prompts, or titles that you want to include with the question
5. When you’re finished with the question, select Done
6. Repeat the above steps for each question that you want to include on the page