The section on Connecting starts on page 16:
https://vmware-tanzu-greenplum-docs.s3.amazonaws.com/VMware+Tanzu+Greenplum+on+AWS+Marketplace+Release+Notes+v6.8.0.pdf
"This is a VMware Tanzu enhanced version of the popular phpPgAdmin web based SQL tool. It has
been configured to start automatically on the Master Instance. The URL is provided in the
Deployment Output. Connection is simple by using the admin "gpadmin" user and the provided
database password."
Also, here's the Troubleshooting guide:
https://vmware-tanzu-greenplum-docs.s3.amazonaws.com/VMware+Tanzu+Greenplum+on+AWS+Marketplace+Troubleshooting+Guide+v6.8.0.pdf