To add the "Star rating" element to your form, you need to click on the selected item or drag it to the right, then you will see the added element on the right:
After you have added the "Star rating" element, click on the "Edit" icon and a pop-up window for editing this element will open in front of you:
In the editing mode, the following fields are available: the total number of stars in the rating (you can choose from 3 to 10), the number of selected stars by default, the rating change mode (half a star, a star and a floating value):
To view an already configured form, click on the "View" icon and the form will open in a new tab in your browser:
The value and description of other fields, you can see here - "The main parameters of the elements".