There're multiple ways to do it.
First method (easy-peasy): Go to Contacts, Click on Add Filter and select the field and associated option by which you would like to filter contacts. On selecting an option, the page will return the list of all attendees who have chosen that option. You can also export them to a CSV file by clicking on Export button.
Second method: Go to Analytics > Custom Reports. Click on New Report to create a report. Choose Contacts and Attendees under user types section. Choose First Name, Last Name, Email and other values under "Choose Associated fields" section. Select a field and the associated option. Remove dates from the date range above and click on Save. Then click on View Report button to view the report and download as CSV.
