To add custom questions to your order form, head to the order form configuration page:
Once you're there, click on the Custom Questions button:
From this screen, you can add up to 10 custom questions. You also have the option to choose different formats for each question:
Question Format Options:
Text field (good for short text responses)
Text Area (good for longer text responses)
Single Checkbox
Multiple Checkboxes
Radios (allows only one answer from the available answer options)
Select List (allows only one answer from the available answer options)
You can also set any of your questions to "Required", which will force the user to answer the question.