1. Create a Trustpilot Developer Account:

   - Go to Trustpilot's developer site (https://developers.trustpilot.com/) and sign up for an account.

2. Register Your Application:

   - Once logged in, create a new application to get your API credentials (API Key, Secret, and Token).

3. Authenticate with the Trustpilot API:

   - Follow Trustpilot's API documentation to authenticate and obtain an access token. You'll need to make a POST request to the Trustpilot API authentication endpoint.

1. Open Google Sheets:

   - Create a new Google Sheet where you want to import the Trustpilot data.

2. Access the Script Editor:

   - Go to `Extensions` > `Apps Script` to open the script editor.

3. Write the Script:

   - In the script editor, write a Google Apps Script function to call the Trustpilot API and parse the response. Here's an example function:

```javascript

function fetchTrustpilotData() {

  var apiEndpoint = 'https://api.trustpilot.com/v1/reviews'; // Replace with the correct API endpoint

  var accessToken = 'YOUR_ACCESS_TOKEN'; // Replace with your access token

  var options = {

    'method' : 'get',

    'headers' : {

      'Authorization' : 'Bearer ' + accessToken

    }

  };

  var response = UrlFetchApp.fetch(apiEndpoint, options);

  var jsonResponse = JSON.parse(response.getContentText());

  // Now, jsonResponse contains the data from Trustpilot.

  // Next, we'll write this data to our Google Sheet.

  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();

  var data = []; // This will hold our rows of data

  // Assuming jsonResponse.reviews is an array of review objects

  jsonResponse.reviews.forEach(function(review) {

    var row = [];

    row.push(review.title);

    row.push(review.text);

    row.push(review.rating);

    // Add other review properties as needed

    data.push(row);

  });

  // Write data to the sheet starting at the first row and first column

  var range = sheet.getRange(1, 1, data.length, data[0].length);

  range.setValues(data);

}

```

4. Save and Run the Script:

   - Save the script and run the `fetchTrustpilotData` function to test it. You may need to give permissions to the script to access your Google Sheet and external services.

If you want to automatically update the Google Sheet with new Trustpilot data at regular intervals, you can use Google Apps Script's triggers.

1. Create a Time-Driven Trigger:

   - In the Google Apps Script editor, click on the clock icon (current project's triggers).

   - Click on `+ Add Trigger` at the bottom right.

   - Choose the `fetchTrustpilotData` function.

   - Set the event source to `Time-driven` and specify the frequency at which you want the script to run.

Trustpilot API might have pagination and rate limits. Make sure your script handles these by checking the API response headers and implementing loops or recursive calls as needed.

Add error handling to your script to manage any potential issues during API calls or data processing. You can use `try...catch` statements and log errors to the Google Sheet or use `Logger.log()` for debugging.

Before finalizing your setup, test the script thoroughly to ensure it handles various scenarios like empty data, API downtime, or unexpected responses.

Remember, the exact details of the script will depend on the specific data you want to fetch from Trustpilot and how you want to structure it in Google Sheets. The example above is a starting point, and you'll need to adjust it based on the Trustpilot API documentation and your requirements.