Add the widget.
Add the question text by typing in the question field.
Add the possible answers by clicking on Option 1 and typing in the answer. You can then hit enter to add a new option or click Add option.
Hover over each of the items to toggle the correct / incorrect switch. If you set more than one correct answer then the radio buttons will switch to checkboxes.
Add feedback to the question by clicking on the edit icon on the right hand side. This will open a context menu with fields for the correct and incorrect feedback.
You can also edit the Submit button text by clicking into the button and typing over it.