When I create a Provider vDC it first ask for a name and on the second page of the wizard I can assign the Provider vDC at the cluster or a resource pool. It is the next section below that states, "The following external network are available to the resource pool you selected:". Although I have several port groups created in vCenter, I do not see anything displayed in this section.
I am also facing the same issue. I will try what you have suggested though. I have been following the vCD Evaluator's guide, the sequence it gives is to create a provider vDC before creating external network. Any comments pls?