At the end of the Field Trial, you will send a survey to your field testers and collect the survey results.
You may use the Google Forms survey template as the basis for your survey. Adapt it to your needs, then send it to your field testers.
Your field testers fill out the survey, and the results are automatically saved in a Google Sheets spreadsheet that you can download.
Once you've collected all the survey results, remove any personally identifiable information (PII). When the Certify page of the Developer Console is available, you will then be able to submit the results to Google.