After clicking on Continue, you will be redirected to the IAM console, to create an IAM role to grant the principal (in this case, Greeter-Audit-Trail, to assume permission to push events to the log group named CloudTrail/GreeterAuditTrailGroup).
This linking is done by AWS, to aid in the seamless integration of CloudTrail with CloudWatch.
After clicking on Allow, you will be redirected to the CloudTrail dashboard, and the integration will be complete. The following screenshot illustrates this step:
The policy document for the IAM role can be viewed by clicking on View Policy ...