After cloning the two repos, you would see two directories: ecs-demo-php-simple-app and ecs-blue-green-deployment.
cd ecs-blue-green-deployment git checkout fargate git branch
From AWS Console, create an S3 bucket for the next step to store CloudFormation templates that will spawn the infrastructure. You may just run the below command from your Cloud9 Terminal:
aws s3 mb s3://<unique-bucket-name>