Hi@akhtar,
You can add one or more tags to a trail, up to a limit of 50. You can also overwrite an existing tag's value when a new value is specified for an existing tag key. The below command can be used to add a tag to a trail.
$ aws cloudtrail add-tags --resource-id arn:aws:cloudtrail:us-east-1:123456789012:trail/Trail1 --tags-list Key=name,Value=Alice Key=location,Value=us