any credentials that you can use to log-in to vSphere client are sufficient.
Can you describe more what you see and what you expect? Maybe post a screenshot? You should see whole vCenter hierarchy with all your datacenters, clusters, hosts and virtual machines. If you click on datacenter or cluster, you should see datacenter or cluster details page with some Top XX resources. If you click on any host, you should get dialog to manage it (add node for the host) or you should get host details page if you have it managed already. There you should see CPU, memory, list of virtual machines etc.