SUMMARY
Customizing a CloudFormation template
ISSUE

After your deployment finishes, you can retrieve the CloudFormation template from the deployment summary. A CloudFormation template is a JSON-formatted text file that describes your AWS infrastructure. If you want to customize the next deployment with AWS console manually, you can modify the template and create stacks with AWS CloudFormation Designer.
TASKS
First, copy the URL from the box on Boomerang. Then Go to the CloudFormation service on the AWS web console(https://console.aws.amazon.com/cloudformation/).

Click 'Design template', it will direct you to AWS CloudFormation Designer console.

Click the file icon on the top left corner. Click 'Open' and choose the 'Amazon S3 Bucket' icon. Paste the template URL and click 'Open'.

After the console finishes loading, you will see the graphical resources infrastructure described by the template.

You can customize the template either by graphical view or text view.
See more details about how to modify template in AWS CloudFormation Designer:
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/working-with-templates-cfn-designer-canvas-details.html
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/working-with-templates-cfn-designer-json-editor.html
After you modify the template, you can click 'Create stack' button to create a new stack.
