Availability depends on course settings. If you don't see this option, ask if your instructor can enable it in their course settings.
We have a new feature available for students needing help from their instructors. And it's available directly in the assignment attempt, referencing both your attempt and the question itself.
To use this feature, you can find it at the top of each question in an assignment attempt.
Here's an example of what the email will look like when sent to your instructor.