S&W tutorial on ec2 - stop redirects to localhost

Hello,
I am going through the Stark & Wayne tutorial, using an aws ec2. I can get to the Concourse CI welcome screen with the instance public ip and port but the login link redirects me to localhost. How do I change the redirect to the ec2 ip?

You have to set the environment var
CONCOURSE_EXTERNAL_URL=https://YOUR URL
Before starting the web process

see https://concourse-ci.org/concourse-web.html