Step 1:
Select Settings -> Registrations
Step 2:
Next select Surveys
There are surveys for single session and multi session.
Step 3A:
Adding a question
Scroll to the bottom of the list of questions and select Add Question
Next configure your new question or add a new field
Configure your new question/field
Step 3B:
Editing a question
Select configure on a question
Edit the available fields
Step 4:
Save the survey