A later exercise will create a simple web server on the "leader" instance that will be created through the examples in this topic. But in order for the web server to work, you will need to open port 80 on the instance. To do this, add a new rule to the security group that is defined in the file securitygroup.tf as described on the page Security Group / HCL Syntax. This rule will be of type tcp. Once you have edited the security group definition, update your deployment by running:

terraform apply

You can view the security group's rules in the Horizon web interface to see your new rule for port 80.