Head over to the surveys page: https://app.surveyapp.io/surveys/ or click the Surveys tab on the main menu:
Locate your survey from the Surveys list, and then click on the three dots to reveal a drop down menu with additional actions.
Click on 'Duplicate this survey' in the menu. You will now be prompted to enter a name for your duplicated survey:
Enter the name for your survey, and click 'Duplicate' to continue.