Here are the remediation steps to ensure that the S3 buckets associated with CloudTrail trails are configured with server access logging:

1. Open the Amazon S3 console.
2. Navigate to the S3 bucket used for storing CloudTrail logs (target bucket).
3. Click on the "Properties" tab.
4. Under "Advanced settings," click on "Server access logging."
5. Click "Enable logging."
6. Choose the target bucket and prefix for the server access logs.
7. Click on the "Create a new S3 bucket" link to create a new S3 bucket for storing the access logs, or choose an existing S3 bucket.
8. Choose the permissions for the access logs S3 bucket, including who can write to and read from the bucket.
9. Click "Save."

Once you have enabled server access logging, you can review the logs to track access to the CloudTrail logs stored in the target bucket. This allows you to monitor who has accessed the data and identify any unauthorized access attempts. Additionally, you can limit who can alter or delete the access logs to prevent tampering and maintain the integrity of the audit trail.