Navigate to the survey feature found under:
menu > dashboard > surveys
From the listing page, you'll see the listing of active or upcoming surveys. Each survey will show you the name, which group of users it applies to, and the number of responses the survey has received. You can edit a survey up to the start time of the survey by selecting the “edit” icon.
From the edit page, you can change any detail of the survey, including the questions. Note that once the survey starts you can't edit it, you can only stop it.