For feedback about questions in students homework
The best way to share feedback is in the Hand-in page.
Navigate to the Hand-in page and select the class and homework week
Click "View" for the student
Click on the question on the left-hand-side
Click "Report an issue with this question"
For all other types of feedback
Click your name in the top-right corner of Sparx and select "Give feedback". Then complete the form to share your feedback.