Set tab order on a section of radio buttons

I have created a form using Adobe Designer and one section has multiple choices but the applicant is allowed to only choose one answer so I used radio buttons for this particular part of the form. How can I set the tabbing order on the radio buttons so the person can tab from the first radio button to the second and so on (the choice they want may be at the end). Right now, they can only use the mouse to move from the first button....hitting the tab key takes them out of the radio button section to the next area of the form.