Firstly, go into the Survey tab in the main navigation menu.
Hover over the survey with the responses you want and click into Reports.
Once in reports, click into Responses
Once in the Responses tab, you have four sub tabs: Responded, Completed, Viewed (Not Responded) and Viewed. To learn more about the difference between Responded and Completed, click here.
Once you've chosen your sub tab, click into the Print/Export drop down menu and export to XLS.